The Toba eruption

Here is a Google Earth image showing part of Sumatra with its capital Medan. The Malaysian coast is at the right with the harbour of Port Klang. Lake Toba, about 100 kilometres long, 30 kilometres wide, and up to 505 metres deep is the largest volcanic lake in the world. Volcanic? Yes, about 74.000 year ago, there was a volcanic eruption, the largest-known explosive eruption on Earth in the last million years. The eruption left a caldera, which is now lake Toba.

There exists a classification for explosive volcanic eruptions, similar to the Richter scale for earthquakes. It is called the Volcanic Explosivity Index (VEI). During an explosive volcanic eruption lots of (molten) rocks and ash (called tephra) are expelled into the air and it is the (estimated) volume of this tephra that is used to classify the eruption. Here is the VEI scale. Like the Richter scale it is logarithmic, each following step means a ten-fold increase in ejected volume. The “How often?” row gives an estimate of the frequency of the eruption, not surprisingly huge eruptions are very rare. There is an older classification of volcanic eruptions, Strombolian, Plinian etc, see Eruption Classifications. The last row gives an estimate of the plume height.

Here are a few examples

The Etna is Europe’s largest active volcano located in Sicily in southern Italy. On average it has a VEI index of 2. I visited this volcano twice, in July 1971 and July 1979. In 1971 it had erupted in April. Lava flows had caused a lot of damage and it was a special sensation to walk over solidified lava that was still hot under your feet. In 1979 it erupted in August but during my visit I still could climb up to the rim of the crater.

The Vesuvius volcano is also located in Italy, near Naples. It is not very active at the moment but erupted in 79 AD. spewing 3.25 km³ of tephra, destroying the cities of Pompeii and Herculaneum. VEI index 5. A catastrophic event.

And that is only VEI-5. Here is the island Santorini in Greece, Or rather what is left of it after a volcano erupted on the island circa 1600 BCE . The eruption volume is an estimated 34.5 km³, so the VEI index is 6. In the center of the caldera two small volcanic islands have been formed. There is still a lot of discussion about the exact date of the eruption, it may have caused the downfall of the Minoan culture.

VEI-6 eruptions are not rare, they occur globally with a frequency of 50-100 years. In 1883 the Krakatoa erupted (8–25 km³ ) . Similar to Santorini, in the resulting caldera a volcanic island, Anak Krakatoa has formed. In this photo seen in the foreground, with Krakatoa in the background.

The most recent VEI-6 eruption was Mount Pinatubo in 1991 with an erupted volume of 12.5 km³ Two photos, one taken about one month after the eruption, the other one taken in 2012, where a lake has formed in the caldera. What a contrast 😉

In recorded history there is only one VEI-7 eruption, Mount Tambora in 1815 with an eruption volume of 144–213 km³ Located on the Indonesian island of Sumbawa, it is now a tourist attraction. The caldera is 6-7 km wide and 600-700 meter deep.

VEI-7 eruptions are so powerful that the plume reaches the stratosphere. This can lead to a volcanic winter event. The lighter particles and ash fall/rain down, but the plume also contains massive amounts of gases like SO2 and H2S which in the stratosphere  react with OH and H2O to form H2SO4 (sulphuric acid) aerosols. They reflect the sunlight, remain in the stratosphere for months or even years and spread globally. The effect is a temporary climate change, affecting crops etc. The year 1816, one year after the Tambora eruption was a Year Without a Summer ! Average global temperature was 0.4–0.7 °C lower, causing major food shortages in many countries.

After this long introduction, it’s time to come back to the Toba eruption. Because it happened so long ago, the estimates of the ejected tephra are of course less accurate, they vary between 2000-13200 km³ A recent one gives 8600 km³. Meaning that the Toba eruption was at least a VEI-8 (more than 1000 km³) and possibly even a VEI-9 (more than 10.000 km³).

How much is 8600 km³? Well, if all that tephra would be deposited over Peninsular Malaysia, it would result in a layer of about 65 meter thick!

When you compare the Tambora eruption with the Toba eruption, Toba should have resulted in a much stronger volcanic winter, possibly lasting many years if not decades.

Could such a volcanic winter have affected our species, Homo Sapiens ? The Toba eruption happened during the Last Glacial Period . It was in that same period that waves of Homo Sapiens migrated out of Africa. This graph shows global temperatures during the last 150.000 years. The Eemian and the Holocene (our present era) are warmer Interglacials. During the Last Glacial Period temperature dropped as did the sea levels. See my blog posts Ice Ages and Sundaland. As you see in the graph, the temperature variations are rather irregular. There are markers for the Out of Africa waves and the Toba eruption

In this map the spreading of Homo Sapiens is shown (in red) together with the distribution of earlier human ancestors, the Neanderthals and the Homo Erectus. In 2012 I did a DNA-test to find out when my ancestors left Africa. For my paternal ancestor that was around 50.000 years ago, my maternal ancestor left earlier, ~70.000 years ago. Both after the Toba eruption. Here is my blog: My ancestors .

The Homo Sapiens population in Africa was small and the migrating groups even smaller, think about numbers in the thousands. They were hunter-gatherers. Sudden climate change might threaten their existence. The Toba Catastrophe Theory, developed a few decades ago, holds that the Toba eruption caused a global volcanic winter, leading to a near extinction of Homo Sapiens, causing what is called a (human) genetic bottleneck. Here is an illustration of a genetic bottleneck. Because only a small number of individuals survives the bottleneck, their genetic diversity is limited.

It is generally accepted that there have been many bottlenecks in the human evolution, Click here for an article about it. And a few months ago Scientific American published an article Human Ancestors Nearly Went Extinct 900,000 Years Ago That was the time of Homo Erectus, long before Homo Sapiens evolved.

The Toba Catastrophe is controversial. Did the Toba eruption produce a bottleneck? Was the Toba Volcanic winter so severe and long lasting that the global population of Homo Sapiens was reduced to about 1000 breeding pairs?

One vocal proponent of the Toba Catastrophe is Donald Prothero, an American geologist , paleontologist and prolific writer In 2018 he published When Humans Nearly Vanished about the Toba Catastrophe.

But here is an equally vocal opponent, John Hawks, an American paleoanthropologist with a popular blog, who wrote in the same year 2018: The so-called Toba bottleneck simply didn’t happen. He mentions research that humans thrived in South Africa during the Toba eruption.

I am not an expert, so don’t expect a verdict from me 😉

Nowadays Lake Toba and Samosir are tourist attractions of Sumatra. Here is a more detailed Google Earth image. Samosir was originally a peninsula until in 1907 a canal was opened through the isthmus.

I have visited Samosir in 1994, thirty years ago, I don’t remember much about it. Peaceful, interesting Batak culture. You don’t realise that you are staying on top of a dormant volcano. Deep below Lake Toba is a huge magma chamber (50.000 km³ ) that is filling up slowly with magma. This has lifted Samosir already around 450 m. Will there be another supervolcano eruption? Yes, but no need to worry, that may take another 600.000 years.

Sundaland

One year ago I wrote a post about the Paleomap Project. At the end of that post I included a link to the Story of the Malay Peninsula. Here it is again. The clip is less than 3 minutes and worth watching.

I ended my post with: Notice how during the Ice Ages the sea-level was so low that the islands of the Malay archipelago were connected. This was called Sundaland. Topic for another post.

Here is my post about Sundaland.

What is actually an Ice Age?

Probably most people will first think about the funny Ice Age movies, but hopefully many will also know that there has actually been a period in Earth’s history, where the climate was cold and a large part of the Earth (North America, Europe) was covered with ice. That was about 21 thousand years ago and it is commonly called the Ice Age. Here is a Paleomap of Earth during that time.

Notice that the map doesn’t say Ice Age, but Last Glacial Maximum ! I got interested, Googled a lot and wrote a separate post Ice Ages. Here is a summary.

  • In the 4.5 billion years of its existence, Earth has been mostly (~85%) a Greenhouse, no icecaps, icesheets, glaciers. But there have also been at least five major periods that Earth was an Icehouse, partially covered with ice. These Icehouse periods are called Ice Ages. At this time Earth is in the Late Cenozoic Ice Age, which started 34 million years ago.
  • In an Ice Age there is always permanent ice, but the amount fluctuates. There are periods that the ice advances, they are called glacials. And there are periods that the ice retracts, called interglacials.
  • The last glacial was about 21.000 years ago and is often called the (Last) Ice Age. At the moment we are living in an interglacial, icecaps, icesheets, glaciers are retracting. But Earth is still an Icehouse.

There have been numerous glacials and interglacials in those 34 million years. Here the global temperatures for the latest are shown. Notice that the timescale is from right to left, so the last glacial (“the Ice Age”) is the rightmost snowflake. And there is an obvious regularity with a period of roughly 100.000 year. If you want to know more about the theory, read the Milankovitch Cycles article in Wikipedia.

In this blog we are especially interested in sea levels. During a glacial a lot of water is frozen in icecaps, icesheets and glaciers, so the sea level drops, and during an interglacial ice melts and the sea level rises. Here are the sea levels during the last 400.000 years. In the original graph time goes from left to right, I have flipped it to make comparison with the temperature graph easier. Notice the similarity between temperature and sea level. During interglacials sea levels were about the same as nowadays, but during glacials they were up to 120 meter lower.

I will now concentrate on the last 150 thousand years, Here is a more detailed temperature graph. Starting from the left, we see the end of the Penultimate Glacial at about 135 thousand year ago. It was a very cold one. Then, relatively quite fast, temperatures are rising, until they reach a maximum at 125 thousands year ago in the Eemian Interglacial. Warmer than nowadays, sea level 6-9 meter higher (!) than today. After this maximum, slowly and irregularly , temperatures are dropping, until a new glacial maximum is reached, about 21 thousand years ago. After this the temperature rises again and we reach the Holocene interglacial in which we are living nowadays.

This time period is very interesting for homo sapiens. Indicated are two waves of migration out of Africa. And about 74.000 year ago the Toba volcano on Sumatra erupted, one of the largest eruptions in Earth’s history. Present day Lake Toba is occupying the caldera of this eruption. There is a theory that this eruption almost caused the extinction of homo sapiens, but this Toba catastrophe theory is something for a separate blog.

We zoom in one more time and look at the sea level. It was 120 m below present during the last glacial maximum, then rising more or less gradually until it reached present levels around 6000 years ago. Around 12-14 thousand years ago, there was an interruption with a cold period (Younger Dryas). Also notice the steep increase around 14 thousand years ago, caused my melting icesheets , about 5 cm per year !

A sea level rise of 120 meter is enormous. Here is a Google Earth screenshot of South East Asia. The color of the sea indicates how deep it is, light blue is shallow, dark blue deep. When you open Google Earth on your computer and move your cursor over the screen, the depth is indicated. I have done that for three locations, and found 50, 30 and 40 meter.

When the sea level drops 120 m, the whole light blue region would become land!

Here is how the region would look like, 21 thousand year ago. Sundaland! A continental shelf, exposed when the sea level is low. If there had been public transport in those days, you could have traveled overland between Indonesia, Malaysia, Thailand, Cambodia en Vietnam! And in the far future, during the next glacial, that will be possible again 😉 .

Here is a video, where you can follow Sundaland from the last Ice Age until present. Only 44 seconds, worth watching. Created by Dhani Irwanto, more about him later.

There are more regions on Earth where something similar has happened. In the lower right part of the video, you can see part of the Sahul shelf. During the last Ice Age Australia and New Guinea were connected.

And in Europe during the last Ice Age, England, Ireland and mainland Europe were connected. The continental shelf is called Doggerland. Around 6500 year ago England became an island (again).

One more example. During the last Ice Age Tamil Nadu and Sri Lanka were connected. In this Google Earth image I have roughly marked the contour line (isobath) of 120 m below sea level. Some land is now submerged but not a continent as some Tamil nationalists still believe. See my blog Kumari Kandam & Lemuria.

Sundaland is a huge landmass (~ 1.8 million km2), now partially submerged. but large during the time that homo sapiens migrated out of Africa. Here are some of these Early Human Migration routes.

1in 2012 Aric and I took part in the Genographic Project , we sent samples of our DNA and got it analysed. It resulted in this map with the routes followed by our (maternal) ancestors. Read my blog My Ancestors for more details.

As you see there are migration routes to South East Asia and Sundaland. Could it be that during this last glacial there was a civilisation in Sundaland, later destroyed by the rising sea levels? Could that have been the lost continent, Plato’s Atlantis? Or the Garden of Eden?

In the last few decades, three books have been published advocating exactly that. In 1999 Stephen Oppenheimer published Eden in the East. According to him it was Sundaland where the first human civilisation started. After Sundaland became flooded (Noah’s flood!), the population dispersed and fertilized the cultures of Mesopotamia, Egypt, China and India. A few years later, in 2005, Arysio Santos published Atlantis, the lost continent finally found. Santos was convinced that Sundaland was the Garden of Eden and Plato’s Atlantis. Quite recently, in 2019, Dhani Irwanto published Sundaland: Tracing The Cradle of Civilizations. Same approach. All these books are still for sale at Amazon.

It’s a fascinating topic, and there is no doubt that Sundaland existed. But Atlantis, the Garden of Eden, the Cradle of Civilisation? Here is some information about the authors.

  • Stephen Oppenheimer (1947-) is a British paediatrician and geneticist. After 1997 he started a new career as a researcher and popular-science writer on human prehistory.
  • Arysio Santos (1937-2005) was a Brazilian nuclear engineer, but “his true hobby in life was researching arcane subjects such as Symbolism, Alchemy, the Holy Grail, Comparative Mythology and Religion” (quote from his own website)
  • Dhani Irwanto (1962 -) is an Indonesian hydro civil engineer. Founder of Indonesia Hydro Consult in 2010 and its director until now. Became interested in Sundaland and has written books about it.

The authors have in common they have no formal training in the subject matter. They were captivated by the subject and delved into all aspects of it, climatology, geology, linguistics, anthropology etc. Their approach, especially Irwanto’s, tries to be scientific. But it is still Fringe Science, outside the mainstream discipline.

I was considering to buy Irwanto’s book, but then I discovered a video Tracing the Cradle of Civilisations in Sundaland, about a lecture he gave in the Philippines in 2017 at an Asean Advanced Archaeology Symposium. Brilliant presentation, worth watching (28 minutes).

But he is really going too far in his enthusiasm. Here is a screenshot from the video. Everything, all over the world , originated in Sundaland. So I may not buy the book.

Ice Ages

What is an Ice Age? And how many Ice Ages have there been on Earth? I came across these questions, while writing a blog post about Sundaland. During the Ice Ages the sea level was much (~ 120 meter) lower than at present and the islands of the Malay archipelago were connected to Thailand, Cambodia and Vietnam. This landmass was called Sundaland. In my blog Sundaland (still under construction) I write in more detail about it.

If what follows is too detailed for you, just jump to the summary

During the 4.5 billion years that Earth existed, Its climate has fluctuated between Greenhouse and Icehouse. During a Greenhouse there were no glaciers, no icecaps (South Pole), no Ice sheets (Greenland) no permanent sea ice (North Pole). Earth was mostly a greenhouse , about 85 % of the time. Temperature was (a lot) higher than at present. Sea levels higher, sometimes 300-400 meter. Lots of carbon dioxide in the atmosphere. Tropical rain forests on the South Pole 😉

But there also have been Icehouses, often called Ice Ages, where glaciers, icecaps and ice sheets were permanently present. Scientists have identified 5 of them. Here they are marked on the 4.5 billion year timescale that Earth existed.

The Hadean, Archean and Proterozoic are the first three “aeons” of Earth’s geological history. We are now living in the last aeon , the Phanerozoic, which started ~ 542 million years ago, the name is too long to be named in the image. Before I “zoom in” on this last aeon, a few comments, related to blogs I wrote in the past.

  • Only a few million years after the formation of Earth, in the Hadean, our Moon was “born” as a result of a collision of Earth with another planet. Where does the Moon come from? .
  • The oldest fossils date back to the Archaean, 3.4 billion years ago, when Earth was still young. Therefore many think that life comes easily and must be ubiquitous in the universe. I am sceptical, see my blog The Drake Equation.
  • It took a long time before those simple cells evolved and developed a nucleus that contained the DNA, about 2,2 billion year ago in the Proterozoic. And it took even longer for multicellular organisms to develop, about 600 million year ago, at the end of the Proterozoic. See my blog The Tree of Life.

The Proterozoic had two Ice Ages. The Huronian actually consists of several separate Ice Ages and lasted about 300 million years The Cryogenian also has two separate Ice Ages, together lasting about 85 million years. The Cryogenian was severe, there may have been periods that Earth was completely covered with ice, a so-called Snowball Earth.

.Keep in mind that Earth looked very different in those days because of plate tectonics and continental drift. See my blog The Paleomap Project. Here is one of Scotese’s maps: Earth during the Cryogenian Ice Age.

Now let’s zoom in on the Phanerozoic, from 542 million year ago until present. The ‘official’ start of this aeon is 538.8 million year ago. This beginning was chosen because around that time a sudden , explosive diversication of life forms started, the Cambrian explosion. Multicellular organisms evolved into a multitude of species. Here is an artist impression.

The Phanerozoic had three major Ice Ages, the Andean-Saharan, 440 million years ago, lasting 40 million years, the Karoo , 300 million years ago, lasting 100 million years and the current one, the Late Cenozoic Ice Age , which started 34 million years ago and is still ongoing.

Here is a (complicated) graph of the global temperature during the Phanerozoic. Complicated because the timeline has been split in five parts, zooming in.

The first part (in red) covers from 542 Million years (Ma) until 66 Ma. The temperature data are less reliable, but you can see the Andean-Saharan (440), the Karoo (300) and an unnamed one (~180). Next comes the green part, timeline enlarged about 10 times, from 66 Ma until ~ 5 Ma. Around 66 million years ago a huge asteroid collided with Earth, causing the extinction of the dinosaurs and giving mammals the opportunity to develop. Earth was a hothouse then with a maximum temperature around 55 million years ago (PETM). After that maximum, global temperature started to decrease. Around 34 million years ago, Antarctica got an icecap and Earth became officially an Icehouse, the Antarctic Glaciation . The next zoom in (again x10, in black) shows how the cooling of Earth continued. Around circa 2.58 million years ago the Pleistocene started, ice “everywhere”, also in the Arctic region.

The next part, in blue, shows in more detail the last one million years of Earth. It’s clearly an Icehouse but there are periods which are colder (glacials) alternating with warmer ones (interglacials). If you would be able to watch Earth during this one million years, you would see the icecaps and ice sheets advancing during glacials and retreating during interglacials. The last of these “warmer” interglacials was the Eemian (130-115 thousand year ago. Followed by the last glacial (26-20 thousand years ago). It is this last glacial that is often, called the Ice Age.

At present Earth is in an interglacial, as can be seen in the last part of the graph (also in blue). This interglacial started around 12 thousand years ago and is predicted to continue for many thousands of years. These predictions are based on the theory of Milankovitch cycles, a bit to complicated to explain here. It may last 50 thousand years, or even longer because of human interference (climate change!). After the interglacial, a new glacial will start, because Earth is still an Ice House.

Summary:

  • Earth is an Ice House already for 34 million years. An Ice House (also known as Ice Age) consists of many glacial (colder) and interglacial (warmer) periods, each lasting thousands of years.
  • The last glacial period occurred 26-20 thousand years ago and is often called the ICE AGE.
  • At the moment Earth is in an interglacial and that will last for many thousands of years, possibly even longer because of human interference.

Of course there is a lot of information available these days about future climate developments. Not always reliable !

Here is a very dishonest one, A New ICE AGE Is Coming: Prepare To Freeze By 2050! A lot of factually correct information, leading to a ridiculous ending. Click on the link to watch the video, AYOR!. His advice: Pump more greenhouse gases into the atmosphere to avoid the impending next Ice Age (~ 2050!).

Here is a much more interesting one, New Evidence We Are Entering An Ice Age Termination Event Glacials have been ended numerous times by termination events. We are in an interglacial now, but it looks different this time. Could this be the start of a Hot House. We just don’t know.

Life on Europa & Enceladus?

It is generally assumed that you need liquid water for life to develop. The planet Mars is now dry and arid, but had lots of water in its far past.. The Perseverance rover (see my blog) is at the moment collecting samples of Martian soil, hoping to find fossil remains of (microbial) life, until now without results. Disappointing for those who are convinced that “simple” life must be ubiquitous in the universe.

When you have been following my blog, you will know that I am not really surprised. Personally I think that (simple) life will NOT develop easily, even in a suitable environment. See my recent post about the Drake Equation.

Are there other places in our solar system with (abundant) liquid water? Yes, there are, here are two, Europa and Enceladus. Europa is a moon of Jupiter and Enceladus a moon of Saturn. Europa is large with a diameter of 3122 km, only slightly smaller then Earth’s Moon (3475 km). Enceladus is much smaller, with a diameter of 504 km. In this image you see the relative sizes of Earth, Moon and Enceladus,

Here are the two moons, Europa left and Enceladus right.. Both moons are covered with a thick crust of water ice. This ice surface has a temperature of about -200 degree Celsius. But underneath this crust both moons have oceans of liquid water!

We think that the interior of the two moons look like this. Europa has a metallic core (iron and nickel),a rocky mantle and a (salty) ocean with an estimated depth of 60-150 km.. A thick ice crust ( 15-25 km) covers the ocean. The model shows the layers to scale.

Enceladus has a rocky core with radius of ~ 180 km , covered by a 30 km deep ocean. and a 20 km thick crust. The ice crust is thinner at the south pole.

How is it possible that these moons have liquid water under their ice crust? Where does the energy come from, the Sun is far way. The answer is: because of the tidal forces exerted by the giants Jupiter and Saturn on their moons.

Newton’s gravitation between two objects depends on the distance between them. For example the gravitational force exerted by the Moon on Earth is stronger on the side facing the Moon than on the other side. This difference is responsible for the tides. The tidal friction will slow down the rotation of Earth , so the length of a day will increase a little bit, about 1,8 millisecond per century. In the far past when the moon was born, the day length may have been about 4 hours only!, For the moon the story is similar: tidal friction has slowed it down, even a lot more, the Moon shows always the same face to Earth, it is “tidally locked”. Actually all the major moons in the Solar System are tidally locked to their planet.

Even tidally locked moons still can undergo tidal flexing, if the orbit is elliptical, a kind of kneading. Model calculations for Europa and Enceladus indicate that this .can generate enough energy to keep the oceans liquid. More (technical) details here.

So both moons have liquid water and a source of energy , two of the essential ingredients for life as we know it. The third ingredient (chemicals like carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus) should be available in the rocky core.

The information about the two moons comes basically from two successful space missions. The Galileo spacecraft arrived at Jupiter in 1995 and stayed in orbit until 2003. It’s main mission was to study the planet, but it managed to have numerous flybys’ of Europa. The Cassini entered Saturn’s orbit in 2004 and stayed there until 2017.

The Cassini mission was very successful, click here for an overview. One of the most spectacular discoveries was that Enceladus is an active moon. There are geysers in the south polar region of the moon! This picture was taken by Cassini in February 2010.

The geysers consist of water vapor and ice particles. The explanation is that water seeps from the ocean floor into the rocky core where it is heated. The heated water rises and erupts though fissures in the icy crust.. It is a bit similar to the hydrothermal vents in Earth’s oceans.

There are indications that Europa also has this kind of geyser activity, although less intense Here is a recent (2021) NASA report, Are Water Plumes Spraying from Europa?

In the search for extraterrestrial life these two moons have top priority. Many proposals for missions to Europa have been formulated and later discarded, here is a list. At the moment the Europa Clipper is being prepared for a launch in October 2024. It will arrive at Jupiter in April 2030. Here is an artist’s concept, of Clipper, Europa and Jupiter. The solar panels of Clipper span 30 meter!

The artist impression might suggest that the Clipper will orbit Europa, but that is not the case, it will orbit Jupiter in an elliptical orbit and make 44 flybys of Europa. It will study Europa’s icy crust, find confirmation for the ocean underneath and try to make flybys through the geysers (if they exist).

A proposed follow-up mission is the Europa Lander. It would land on Europa, collect some material from the icy crust and search for biomarkers, signs of life. Here is another artist impression. Notice the geyser at the horizon 😉 .

Probably the Europa Lander mission will be cancelled. Why? Because Enceladus offers better options than Europa. The main difference is that Enceladus is continuously spewing water and ice crystals, whereas the geysers of Europa are sporadic and still have to be confirmed.

The reason that there is so much interest in the geysers is obvious. To find out if there is life in these oceans, we have to drill through a 15-25 km thick ice crust first. Actually there are studies how to do that, they read like science fiction. Here is the final report (pdf file, 70 pages, 2019) about the Europa Tunnelbot. The basic idea is that this tunnelbot would melt itself down through the ice crust of 20 km in 3 years time, to reach the ocean. Here is a artist impression from the report, I have rotated it 90 degrees, to fit better in this post. Left is the icy surface of Europa, the inset shows three “repeaters” because even when the bot reaches the ocean it still must transmit date to the lander.

Science fiction and I think it will never happen, because the geysers on Enceladus and possibly on Europa may already give information about life in the oceans below the crust!

After Cassini observed the geysers on Enceladus, the scientific program was adapted and the spacecraft went a few times through the plumes. It found water, ice crystals and organic compounds!

So that will be the program for the next decades, explore Enceladus and find out whether the geysers will have convincing biomarkers.. .

Of course it will take time to design Enceladus missions. Here is one, the Enceladus Orbilander. Approved as a so-called Flagship Mission. Still in the design phase. possible launch in the late 2030s Arriving at Enceladus in the early 2050s.

First it will fly numerous times through the geysers, collect material and analyse it. Then it will land at the South polar region.

This is the South polar region of Enceladus. The “tiger stripes” are fissures in the ice crust where geysers erupt.

And here is an artist impression of the Orbilander on the surface of Enceladus.

Until now life has only be found on Earth. Discovery of (primitive) life elsewhere in our solar system would be dramatic, because in that case we would know that (intelligent) life is ubiquitous in the universe.

At the moment Perseverance is collecting soil samples on Mars which will be brought back to Earth by the Mars Sample Return Mission around 2033. At about the same time Clipper will explore Europa. So we will have to wait for 10 years and for results from Enceladus about 30 years.

The Drake equation

In 2019 I wrote a blog post A Pale Blue Dot with these two pictures in it. Left the iconic picture of Earth, taken  in 1972 by the crew of the Apollo 17 spacecraft, on their way to the Moon. Right a picture taken in 1990 by the Voyager 1, leaving the solar system and looking back to Earth At 6 billion km only a pale blue dot.

Earth is our beautiful world, one of the eight planets in the Solar System and the only one where life has developed, as far as we know.

Are there other worlds in the Universe? Our Sun is one of about 100 billion stars in the Milky Way and the MIlky Way is one of an estimated 200 billion galaxies in the (observable) universe.

The left picture shows the spiral structure of the Milky Way, with the location of our Sun marked. The right picture is the famous Ultra-Deep Field image taken in 2003 by the Hubble telescope. The image shows an estimated 10.000 galaxies in a part of the sky with a diameter 1/10th of the moon.

In 1992 the first extrasolar planet (exoplanet) was detected, at the time of writing this blog more than 5000 have been found and it is now assumed that most stars will have at least one planet orbiting it. That means that in the Milky Way alone there are already billions of planets.

Wouldn’t it be strange if Earth is the only planet where (intelligent) life has developed? There could be numerous planets in the Milky Way and Universe where life has developed. Michio Kaku an American ‘science communicator’, who always enjoys being in the limelight, goes even further: “The Laws of Probability Tell Us That the Universe Should Be Teeming With Intelligent Life Forms” 

The Laws of Probability ? As usual I am a sceptic. In 2010 I wrote two posts about “Are we alone in the Universe“. My personal opinion at that time was: “Yes, we might well be alone“. Now, thirteen years later, my opinion is still the same, maybe even stronger.

After this lengthy introduction, time to go back to the topic of this post, the Drake Equation.

Speculation about extraterrestrial life dates back to antiquity. Around 1900 it was thought by many that the planet Mars had irrigation canals, built by intelligent beings. Development of more powerful telescopes showed that those canals were an illusion. But maybe there were intelligent beings outside our solar system? This led in the 1960’s to the SETI program. the Seach for Extra-Terrestrial Intelligence. Involved in this program was Frank Drake, a young American astronomer. To have discussion points for the first scientific SETI meeting, he came up with what is now called the Drake equation.

Actually it is NOT an equation, it is an estimate for the number of intelligent civilisations in our Milky Way. The idea is simple, you start with how many stars are born yearly in the Milky Way. How many of these stars will have planets, how many of these planets will be suitable for life, how many of these suitable planets will actually develop life. How many planets with life will develop civilistations (intelligent life), and how many of these civilisations will be able/willing to communicate with us. And finally, how many years will such a civilisation survive.

Here the Drake equation is visualised: The estimated number of intelligent civilisations in the Milky way who can communicate with us is given by N as the product of a number of factors.

R* = how many stars are born every year in our galaxy. (R = 1 yr−1)

fp = the fraction of these stars that have planets. (fp = 0.2 to 0.5)

ne = the average number of planets in the habitable zone of such a star (ne = 1 to 5)

fl = the fraction of habitable planets that actually develop life. (fl = 1)

fi = the fraction of those planets, where evolution leads to civilisations with intelligent life (fi = 1)

fc = the fraction of these civilisations that develop a technology capable of releasing detectable signs of their existence into space. (fc = 0.1 to 0.2)

L = the length of time that such a civilisation will exist.(L = 1000 -100,000,000 years)

In the 1961 discussion the various factors were discussed. I have given these estimates above. Using the lower limits, it gives a minimum of N ≈ 20 technological;y advanced civilisations, who could send signals to us. If those civilisations have not self-destructed, L could be many millions of years resulting in maximum of N ≈ 50.000.000 !

With this evaluation you will understand that it made sense to start the SETI program. After a few years a distributed computing project SETI@Home was started, where volunteers could use the idle time of their PC’s to analyse data from radio telescopes, searching for signals. of intelligent life . Many years I have taken part in this program. My PC during idle time was doing this.

After about 20 years the program was stopped, without any results. But in 2016 a follow-up project started Breakthrough Listen. Basically the same as SETI, but much more powerful, it will generate as much data in one day as previous SETI projects generated in one year. Until now no positive results.

I ended my 2019 post with :”As soon as evidence of life will be found, on Mars or deep under the frozen oceans of Jupiter’s moon Europa, I will celebrate and be convinced that life indeed is teeming in the Universe. Until then, I believe in the Rare Earth Hypothesis , that we might well be alone.

What is this Rare Earth hypothesis? In 2000 Ward and Brownlee published a book Rare Earth: Why Complex Life Is Uncommon in the Universe in which they argue that primitive (microbial) life may be common in the Universe, but that complex (intelligent) life is probably very rare.

I agree with them that complex life will be rare in the Universe, but I no longer think that primitive life will be common.

A few months ago I published a post Perseverance perseveres about the Mars rover who is looking for traces of past life on the planet Mars. The scientists were expecting/hoping to find stromatolites, fossils of microbial life formed in the time that Mars had water. Something similar to this, found in Australia, 3.4 billion year old.

Until now no sign of fossil microbial life has been found. So it could be that the chance that primitive life develops on a planet in the habitable zone is also small!

As long as no sign of (fossil) microbial life is found in our solar system or elsewhere, I think that even primitive life may be rare in the universe. I used to say, We may be alone in the Universe. I now go one step further:

We are probably alone in the Universe

But of course I hope that I am wrong

Perseverance perseveres

On 18 February 2021 the Perseverance rover landed successfuly in the Jezero crater on planet Mars. A few weeks later I wrote a detailed blog about the landing and the mission of the Perseverance: to determine whether Mars ever was, or is, habitable to microbial life. We are now more than two years later, time to give an update. I assume that you have read the first post ;-).

First about the Ingenuity helicopter. There has been a lot of opposition to include the helicopter in the project, many people were worried that it might compromise the main goal of Perseverance. Here are two pictures taken by the WATSON camera (mounted on the robotic arm). Left the Ingenuity still under Perseverance’s belly with its legs unfolded, right next the the rover, ready to fly. Photos taken 1 and 7 April 2021, respectively

Here is a selfie of Perseverance, taken on 6 April 2021 again by the WATSON camera. Notice how small the helicopter is. Do you wonder why you don’t see the robotic arm in this picture? Actually WATSON took 62 pictures, resulting in this composite image, click here for details.

Originally only 5 flights of Ingenuity were planned, just to test if the helicopter could fly in the very thin Martian atmosphere. Because contact with Earth takes about 11 minutes, those flights have to be autonomous. They were so successful that the Ingenuity is still operating now, on 23 April it had its 51th flight. It is actually scouting for Perseverance to find suitable locations to explore. Click here for a list of all flights, full of interesting details. During flight 51 Ingenuity took a picture of Perseverance (upper left corner). Not easy to spot, the right picture shows an enlargement

In my Perseverance blog, I could only be rather vague about details of the mission. The rover was supposed to collect samples of Martian rocks and soil (regolith), using the drill on its robotic arm. Then put these samples in sample tubes and store them in a container. Here is an example of a sample tube, the container can hold 43 of them.

Here is the proposed route at the time when I wrote my blog.. The x marks the landing of Perseverance in the Jezero crater, which was a lake, billions of year ago. In those days a river was flowing into the lake (from the left), creating a delta of sediment. If ever life developed on Mars, this region might be suitable to find proof of it.

And here you see the actual route of the rover during the last two years. It is a screenshot from the NASA website Where is Perseverance? Really worthwhile to visit the site, you can zoom in on the map which is updated regularly. The red markers give the locations where samples have been collected. The blue markers show where the Perseverance and the Ingenuity are.

When you visit the website and zoom in, you will get this. Clicking on a white circle will tell you when the rover was there, clicking on a line segment gives the distance, clicking on a red marker will tell you the number of the sample collected

During the two years that Perseverance has been exploring, it has collected 19 samples, here is the list, with lots of details for each sample.

The first sample was actually a failure, it must have been a shock for the team! Here is a screenshot. Sample Type: Atmosopheric. The core must have been too powdery/brittle, broken into pieces, and the capsule is empty. More about it here .

Fortunately all other sampling attempts until now were successful. Here is an example. The rocky outcrop has been named Wildcat Ridge. Two samples (no 12 &13 in the list) have been drilled and a circular patch of the rock has been abraded to investigate the rock’s composition.

Why two samples from the same location? When you look at the list, you will find that this is the usual procedure. All samples have been collected twice from each location (except the first, failed, one).

In the period between 21 December 2022 and 28 January 2023, one sample of each location has been dropped in what has been called a depot, named Three Forks. I have indicated the location with a red oval in the detailed map above. Here is a picture of the second sample being dropped.

And here is a collage of all 10 samples dropped. THe Atmospheric sample, 8 samples with rock or regolith and one witness sample. A witness tube will follow the same procedure, but not collect any rock or regolith. Back on earth it will be inspected to check for any contamination with material from Earth. Click here for more details.

,The sample tubes tubes are not dropped at the same spot, but about 5-15 meter apart. The center of each circle is the location where that sample was deployed, with in red the name given to the sample (see the list).

Why all this? Basically for safety reasons. The ultimate goal of the mission is to bring the sample capsules back to earth, where they can be studied in much more detail than is possible by Perseverance. In my first blog I wrote that this so-called Mars Sample Return porject at first sight looks like science fiction. And I still think it does 😉 . Here is an outline of the project in its present form.

  • In 2027 the Earth Return Orbiter (ERO) will be launched and reach Mars in 2029 where it will go in orbit and wait for the container with the samples.
  • In 2028 the Sample Retrieval Lander (SRL) will be launched. It will land on Mars in 2029, probably close to the Three Forks depot. It will bring two helicopters and the Mars Ascent Vehicle (MAV), a rocket.
  • If Perseverance is still working properly, it will also travel back to the Three Forks depot. In that case it can transfer its samples to the MAV
  • If not, the two helicopters will transfer the ten dropped samples to the MAV
  • After the samples have been stored in the MAV, it will leave Mars, go in orbit around the planet and release the container with the samples.
  • The ERO will pick up the container with the samples and place them in the Earth Entry Vehicle (EEV). Then it will leave its orbit and travel back to Earth
  • Near Earth the ERO will release the EEV which will “fall” back to Earth. No navigation, no parachute. It is scheduled to land in 2033 in the desert sand of the Utah Test and Training Range.

In this artist impression the Sample Retrieval Lander is at the right, left the Perseverance. The Mars Ascent Vehicle has just been launched, it will bring the container with the precious samples to the Earth Return Orbiter. One of the Sample Recovery Helicopters is hovering in the thin Martian atmosphere.

In the original design, the Sample Retrieval Lander carried another rover which transported the sample tubes from Perseverance to Mars Ascent Vehicle. . It has been skipped because of the success of the Ingenuity helicopter. The Sample Recovery Helicopter has basically the same design, but is stronger, can carry a small load and has wheels. Here is an artist imprssion. It can transport a dropped sample tube, one at a time, from the depot to the Lander.

.Another design change is that the Sample Retrieval Lander has a powerful robotic arm to put the samples in the sample container. Have a look at this fascinating video. The robotic arm picks up a sample tube from the ground, and puts it inside the rocket. But it can do the same with samples stored inside the Perseverance.

Have a look at this animation. You see the Sample Retrieval Lander land near the Perseverance. The robotic arm transfers the sample capsules to the Mars Ascent Vehicle, which is then launched. When in orbit it releases the container with the samples. This container is then collected by the Earth Return Orbiter. There the container will be placed in the Earth Entry Vehicle. All this will take place after the landing of the Sample Retriever Lander in 2029.

At the moment the whole whole retrieval mission is still in the design phase. Here are prototypes of the sample container and the Earth Entry Vehicle. To give you an impression of the size, a sample tube is about 15 cm long. The container is roughly the sise of a basketball. The diameter of the EEV will be about 1.5 meter.

The retrieval operation will take place in 2029, six years from now. The Perseverance is working beyond expectation, but will it still work properly in 2029? In the first phase of the exploration Perseverance has collected dupilcate samples and dropped one of each at the Three Forks depot. In one of the NASA reports I read that in the second phase the Perseverance will no longer collect duplicates.

So, when everything goes well, in 2029 Pereverance will return to the Three Forks Depot with in its belly around 30 collected samples. In that case The Robotic Arm will transfer the samples to the sample container. It will leave the depot untouched! Why? Because the retrieval will be a risky process. The container after launch will be floating in orbit and hopefully collected by the Earth Retrun Orbiter. And near earth the container, now inside the EEV, will be dropped near Earth and hopefully fall down in the Utah desert. I still think it’s science fiction 😉 So, in case something goes wrong, at least there are still 10 samples in the depot, waiting for another mission.

The paragraph above is my own interpretation.

And this is my personal comment, before I finish this blog.

The whole mission until now has been presented as a huge success. And techologically speaking, I agree. But still I think the scientists will be a bit disappointed, because a “smoking gun” has not been found until now.

When (microbial) life developed on earth, 3.5 billion year ago, it left fossil traces behind, called stromatolites, like this one, found in Australia..

If this kind of sediment would be found in the Jezero crater om Mars, it would be frontpage news all over the world: Life has existed on Mars.

In 2019 a team of NASA/ESA scientists went to Australia to study the stromatolites. In the video they call them the Holy Grail.

But until now no sign. The collected samples contain organic molecules, but that is nothing new, Curioisity, the predecessor of Perseverance already found them.

Of course Perseverance will persevere exploring the sediments in the Jezero delta and collect more samples. Hopefully it will one day be able to take pictures of stromatolite. If not then we will have to wait until 2033 when the samples are returned to Earth and can be investigated in specialised laboratories.

Yes, I think the scientists are a bit disappointed.

Me as a Student

A few weeks ago I published a blog post Me as a Physics Teacher. Searching my archive for photos, I came across several pictures taken during my “student” days. So here is a post about my life as a student.

Here is the only photo I have about the start of my “student” life 😉 Taken when I was 5 year old, during my stay at the kindergarten school.

Some photos must have been taken during my primary school time, but I cannot find any in my archive. My results were good, I skipped a class and was only11 year old in 1955 when I went to the Christelijk Lyceum in my hometown Alphen a/d Rijn. In those days a Lyceum was a school type with two courses, a five year one (HBS) and a six year one (Gymnasium). The Gymnasium stream had Greek and Latin as additional languages (besides Dutch, English, German and French) and prepared for university.

I was admitted to the Gymnasium stream. Here is my 2 Gym class in 1956-57. I am standing, fourth from the right.

One year later, class 3 Gym. I am standing in the back row, third from left. Next to me my best school friend Bram and my physics teacher Smit, who played an important role in my decision to study physics.

Our Gymnasium class was already quite small, but in class 5 Gym it was split in two, Alpha and Beta. The alphas got more Greek and Latin, the betas more mathematics and science. Here is the small 5 Gym Beta class with our Greek language teacher Flink. He was a nice old-fashioned gentleman, and we accepted willingly the awful smell of his pipe tobacco (smoking in the classroom was still permitted in those days). Can you find me? Sitting in the center, next to my friend Bram.

The usual school photo, in class 5 Gym Beta. February 1960, I am still 15 year old, will be 16 in April.

The final examination for Gymnasium classes was quite special in those days. In addition to the written tests, there was also oral ones, taken by your teacher and a university professor. After an exciting day, the end result was discussed by teachers and visitors in the staff room. We had to wait in a classroom for the verdict. Luckily in our small group everyone passed.

Time to celebrate, here in front of my family house.

Many of us continued our studies at various universities. The famous Leiden University was close to my hometown and a logical choice, but I was the first in my (extended) family to go to university and my parents preferred the Christian Vrije Universiteit in Amsterdam. They managed to find lodgings for me with a nice (Christian) landlady. I was only seventeen year old, in retrospect too young.

I enrolled for physics and mathematics. and I also joined the student corporation of the VU. In those days the student corpora had severe initiation rituals. The aspirant members had their head shaven and were humiliated in many ways a couple of weeks, before they were accepted. Here is a picture I found on the Internet, taken in 1961. I still vividly remember the experience.

At the end of 1961 a few of my classmates had a kind of reunion. Our favorite teacher of Dutch language, Miss Dubbeldam, was also present. Notice that my hair is growing back already, pity that I don’t have a picture when my head was clean shaven.

My room in Amsterdam was actually a kind of garden house. Private, but to reach it, I had to pass through the house of my landlady. Here I am standing in front of my rooms, around 1963. I did not really enjoy those first years at university, as soon as the lectures finished (Saturday morning!) I took the bus back to my hometown and stayed there with my family until Monday morning.

After I was accepted in the student corporation, I became a member of the sorority (“dispuut”) Odysseus. Weekly we met for drinks and there were regular meetings, where you could train/show your oratorical skills. A nice “cultural” dispuut, but still too macho for the immature guy I was. After a few years I left the club.

I had a few good friends. One of them is Nellie, we first met when we were both freshmen, more than 60 year ago. Here I have joined Nellie at a party of her :”dispuut” Notice how formally dressed I am, in a three-piece suit..

I was a diligent student. On the wall of my room the certificate that I was a member of the student corporation.

In my room with some more friends. Jan, my best friend in those days, is trying to sing something from Bach. We were a serious bunch.

Pictures taken at the same time. I had bought an old piano and was still following piano lessons in my hometown. It must have been a party, with the bottles stored in the piano, but I don’t remember what we celebrated. .

In those days university studies were split in two parts , the “kandidaatsexamen” and the “doctoraalexamen”, more or less equivalent to present day Bachelor and Master degrees.

I passed my “kandidaats” in 1965. In those days taking four years for this degree was quite normal. For the second phase, we had to follow lectures, pass tests, but also .work in the physics laboratory, taking part in excursions to other universities etc. I chose nuclear physics as a specialism and worked in a group, led by Anne de Beer, who was doing research for his PhD thesis. A very enjoyable few years

In 1967 I took part in a trip to the UK where we visited several laboratories

At the end of the trip we enjoyed a nice dinner. Notice that we are smoking cigars.

At the end of 1967 an important event took place in my life, resulting in a big change in my outward appearance. It was hippie time, my hair grew longer, my clothing became informal and I got interested in popmusic. See my blog Musical Nostalgia.

In those days military service was still compulsory, but you got a deferment if you studied. In 1968 I was given a test to determine whether I had leadership qualities. It was fun, here I am (no 26), I didn’t try to qualify because I had already decided to become a conscientious objector in case I had to go into military service.

Anne, the leader of my group defended his dissertation on 20 December 1968. He asked me and another student to be his paranymph, an old tradition. Formally dressed in white tie, but with long hair, I was of course subject to funny remarks.

A few months later I obtained my doctoraalexamen (Master of Science degree), I became a doctorandus .My university asked me if I would like, to stay , get a part-time job as scientific assistant and do research for a Ph.D. .I was honored and accepted. As my interest was more in theory than in experiments, it was decided that I would do research in theoretical nuclear physics.

Although I was no longer a student, I was still entitled to a student identity card

For various reasons it took me a rather long time to do my research and write my thesis. Here are a few pages of my thesis.

Here I am defending my thesis, 2 September 1976. Paranymphs were no longer needed.

It was a public ceremony, colleagues from the physics faculty were present, my proud family on the first row. My physics teacher from the Lyceum was there (second row, second from right), I had already accepted a job as physics teacher and started a few weeks earlier. The principal of my new school was there and a teacher colleague with a few young pupils from one of my classes (one row below the top row, in the middle).

That was the end of my academic career, although I still published an article about my research in 1978

The Pillars of Creation

In 1995 NASA published this picture, taken by the Hubble Space Telescope. It shows a small part of the Eagle Nebula and became instantly famous. Because in the “pillars” stars are born, the picture got the name “Pillars of Creation”.

The Hubble Space Telescope was launched in 1990 and is still operating, with quite a few Space Shuttle service missions. To celebrate its 25th anniversary, a new picture of the Pillars of Creation was published in 2015. With a new camera installed, more details are visible,

At the same time this picture was published, an infrared picture of the Pillars. Infrared light can travel more easily through dust and clouds and that is why now you see stars in the pillars, where young stars are still being formed. But I hope you wonder how this can be an infrared picture as infrared light is invisible light. The explanation will be the main part of this post.

But first here are two pictures, recently taken by the James Webb Space Telescope. The JWST is an infrared telescope has and has two cameras on board to take pictures. The NIRCAM for near infrared light and the MIRI for medium infrared light. Here is the NIRCAM photo

And here is the image from MIRI, Amazingly different. And again, how can these be infrared pictures’?

Time to give some explanation about the pictures and also about the Eagle Nebula, where the Pillars of Creation are located.

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About visible and invisible light

Light is an electromagnetic wave, as are microwaves, radio waves, X-rays etc, They all have different wavelengths. The wavelengths of visible light are often given in nanometers (nm), where 1 nm is 1/billionth meter. Or in micrometer (μm) where 1 μm = 1000 nm. The human eye is sensitive to wavelengths between ~380 and ~750 nanometer and sees the various wavelengths as different colors! The longest wavelengths are seen as red, the shortest as purple/blue with all the “rainbow” colors in between.. In this diagram the electromagnetic spectrum is shown. The infrared part can be subdivided in near infrared, mid infrared and far infrared

The Hubble telescope has two cameras onboard. Most of the iconic Hubble pictures have been taken by the Wide Field Camera. The present wide field camera (WFC3) can take photos in two channels, one for ultraviolet and visible light (UVIS) and the other one for near infrared (NIR), The range of UVIS is 200-1000 nm and of the NIR 800-1700 nm

The James Webb has two cameras, the NIRCAM for the near Infrared, range 600-5000 nm and the MIRI for the mid Iinfrared, range 5000-28000 nm (5 μm -28 μm).

Before we describe in some detail how digital cameras record images, it is useful to have a look at the way the human eye sees colors.

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How does the human eye see colors?

The retina of the human eye contains about 6 million nerve cells, called cones. These cones come in three different types, S, M and L, sensitive to various parts of the spectrum. The S type cones are sensitive to the blue part of the spectrum and are also often called Blue cones, In the same way the other two are often called Green and Red.

The brain is able to combine the response of these RGB- cells. For some people the M and/or L cone cells are not working properly. As a result they are colorblind.

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How does a digital camera record colors?

Digital cameras have sensors consisting of millions of individual pixels that record the intensity of the incoming light, basically in a gray scale (black and white). That these cameras can take color pictures is because in front of the sensor there is a color filter, consisting of a mosaic of millions of red, green and blue “pixels”. A so-called Bayer filter. See the diagram below. Taking a picture, means actually taking a red, green and blue picture at the same time, but these pictures are “incomplete”. By mathematical techniques (interpolation) the full color pictures are constructed.

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Here is an example, where three images, in red, green and blue, when combined, give the full image in natural colors.

The sensors in space telescopes do not have these Bayer filters, they just record the image in gray scales. However, various filters can be placed in front of the sensor and multiple images can be taken of the same object. For example, the Hubble WFC3 camera has a huge choice of filters, 47 for the UVIS channel and 14 for the IR channel.

Why so many? Some filters are broadband, they pass a wide range of wavelengths. From a scientific point of vew the narrowband filters are interesting because they pass only the light emitted by specific elements. Here is one example, hydrogen (H) emits red light with a very specific wavelength of 656 nm. So one of the filters only passes wavelengths around that value and a picture taken with this filter shows the presence of hydrogen. Similar filters can be used to check the presence of oxygen (O), sulphur (S) etc.

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The Pillars of Creation pictures are “false-color” pictures!

On 1 April 1995, astrophysicists Jeff Hester and Paul Scowen published an article The Eagle Nebula, in which they showed a picture of the Pillars of Creation. If you think that was “just” a picture taken by the Hubble telescope, you are seriously mistaken. The PBS/NOVA website More than just a pretty picture explains in 19(!) webpages how the iconic photo was created. Very readable,

The WFC2 consisted actually of four cameras, each recording a quadrant. The top-right quadrant camera was slightly different, zooming to show more details. Resizing it to the format of the other three, causes the characteristic Hubble image with the “steps” in one corner. Here is the original image of this top right quadrant, in gray scales. What a mess. For an explanation how to clean this image, see the website. The second image shows the result of the various cleaning operations. What a difference !

We can do the same for the other quadrants.

Now we can “glue” the four parts together. You can still see a bit the seams between the four images.

For this mage a filter was used that only let blue-green light through from (doubly ionised) Oxygen atoms (OIII). Two more filters were used to create images in the same way. One filter let only the reddish light from Hydrogen atoms through (Ha), the other one selected reddish(!) light from ionised Sulphur atoms SII). Three narrowband filters, two of them in the same color range.

Here are the three filtered images

You might expect that the next step would be to give these image’s color corresponding to the filter used for each of them. The Ha and SII reddish and the OIII one greenish. But that is NOT what Hester and Scowen did. They assigned the RGB colors to the three images. Blue to the OIII image, Green tot the Ha image and Red to the SII image.

Final step is to combine them: the Pillars of Creation.

The main reason to assign “false colors” to the pictures is to enhance the contrast and to see how the various elements are distributed. Almost all Hubble photos are false color (also called pseudo color). Using the three narrowband filters for S, H and O and assigning them to RGB is so common that it is often called the Hubble Palette. Doing a Google image search for Hubble Palette gives a huge number of hits. Here is a part.

Other combinations of narrowband filters are also used. Here is an example where 6 filters have been used for the Butterfly Nebula. Besides SII, Ha and OIII, also ionised nitrogen, helium and oxygen. In the table the natural colors are given and also the colors assigned in the Hubble palette.

An American astrophotographer got curious how this nebula would look in the natural colors. Here are two images’, left the false color one and right the picture in natural colors. It is clear that the artificial image reveals many more details

It must be clear now that while with the Hubble telescope you have a choice to use false colors, with the JWST there is no other option, as infrared light is not visible. Here are the filters used for the MIRI camera. The colors suggested for the various infrared ranges are not significant, just to guide the eye.

For the MIRI picture three filters were used, F770W, F1130W and F1500W. In the above diagram I have marked them. For this picture they are assigned Blue, Green and Red respectively.

The NIRCam camera has many more filters, broadband, narrowband etc.

For the NIRCam picture 6 filters have been used, marked in the diagram above.

I have read somewhere that creating these images should be considered as art and I agree.

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The Eagle Nebula

Finally a few remarks about the Eagle Nebula. When massive stars die, they can “explode” as a supernova, erupting their remnants into space. In these clouds of dust and various elements, new stars can be formed. The Eagle Nebula is such a cloud, here is a picture taken by an astrophotographer, using a telescope and a DSLR camera! Many of the bright spots in this picture are young stars already formed in the cloud. These stars are so hot that they emit UV light and even X-rays. This radiation can has enough energy to ionize the cloud. Such a cloud is called an emission nebula. The dominant reddish color is caused by hydrogen

The Eagle nebula is located about 7000 lightyear away and is huge, roughly 70 x 55 lightyear. It is a young nebula, estimated age is 5.5 million year. It is also a temporary event, the forming of new stars still continues and the radiation those stars will erode the nebula.

In the center of the above image, you can see the pillars of creation.Here is a dteail. Comapre it with the images of Hubble and Webb. Even these pillars are huge, the logext one is about 4 lightyear long.

A final remark. From the Hubble and Webb picture you might think that the pillars are almost like rock, impenetrable. But this is not true at all. The density of nebulas varies between 100 – 1 million particles per cubic cm. A high vacuum on earth still has considerably more particles per cubic cm. It is just the huge size that makes the pillars look like solid.

The Paleomap Project

INTRODUCTION

Twenty years ago I started my own website. Although now in hibernation, this Stuif Site is still online. It has a Science -> Earth category, here is a screenshot of that page. I was quite interested in plate tectonics and continental drift and was planning to write more webpages about it. This never happened, the Earth page remained a “stub”.

But finally I have now decided to write a blog.

Recently I came across an article The Lost Continent of Kumari Kandam in which I found this map: I had never heard about Kumari Kandam and had to check Wikipedia: Kumari Kandam, “a mythical continent, believed to be lost with an ancient Tamil civilization

Apparently some Tamil revivalists still think that this continent really existed and actually was the cradle of civilisation, not Mesopotamia . The continent was submerged after the last Ice Age, when sea levels rose, forcing the Tamil people to migrate to other parts of the world. And yes, the sea levels rose after the last Ice Age, more than 120 meters. But have a look at the Google Earth nap of the Indian Ocean, where I have outlined Kumari Kandam. Mean sea depth is ~ 4 km!

So the Kumari Kandam continent never existed. A few months ago I have written a separate blog about this myth: Kumari Kandam & Lemuria .In that post I announced a post about continental drift and plate tectonics. Here it is.

THE STRUCTURE OF EARTH

When Earth was formed, 4.55 billion year ago, it was in a completely molten state. The heavier elements sank to the center, the lighter elements rose to the surface. Because of cooling soon a crust developed. Here are two images of present Earth , showing its structure. Basically there are three main layers, the Crust, the Mantle and the Core.

The Core consists mainly of iron and nickel. In the Outer Core they are liquid (high temperature) and are the source of Earth’s magnetic field. The Inner Core is solid, the temperature is even higher, (about 6000 °C) but the pressure is gigantic.

The mantle is basically solid, but the upper mantle is already so hot, that it behaves as a fluid on a timescale of many millions of years. This upper part is called the Asthenosphere. .

The right image gives more details about the size of the various layers. The crust of Earth is very thin, especially under the oceans (~6-7 km). The continental crust is much thicker , 30-70 km and less dense than the oceanic crust. Compare the Earth crust with the shell of a chicken egg, or the skin of an apple

The crust of Earth is not one whole, it is broken in many separate parts, called tectonic plates. Below you see the main tectonic plates at present. They “float” on the mantle, very slowly, about a few cm/year. Red arrows indicate the direction in which they move.

A few comments on this map

  • In the Atlantic Ocean the Eurasian plate and the North America plate move in opposite directions, creating a gap, that is filled by magma from the underlying mantle. They are called Mid-ocean ridges.
  • The Eurasian plate and the Indian plate collide, resulting in the Himalayas.
  • The Australian plate and the Pacific plate also collide, but here they create a Subduction zone. Because oceanic crust is denser than continental crust. the oceanic crust will go down under the continental crust and merge again with the mantel.

Two images as an illustration: a mid-ocean ridge (left) and a subduction zone (right)

These examples show that plates can change in time, they can also merge or split. In the past Earth has looked different, and in the future it will also look different.

THE PALEOMAP PROJECT

A paleomap is a map of Earth in the past, using information about tectonic plates. The American geologist Christopher Scotese started the Paleomap Project in the 1990s and is still actively working on it. Here are a few of his maps

This is a map of Earth, about 200 million year ago. In that period most of of the landmasses were connected and formed a supercontinent, named Pangaea. In the lower part, called Gondwana, you can already see the shapes of present-day Africa, South-America, Antarctica and Australia

Millions of years later, Pangaea has broken apart. Dinosaurs are roaming the earth

Earth starts to look a bit more familiar South-America and Africa have split, with the southern Atlantic Ocean separating them. Eurasia begins to take shape. Australia is still connected to Antarctica. Note that India has split from Africa.

Earth 66 million year ago. The impact of the Chicxulub meteor in Mexico causes the extinction of the dinosaurs and the rise of mammals. India is on a collision course with Asia and Australia has split from Antarctica.

Present Earth..

More maps can be found here. The oldest map shows Earth 513 million years ago

These are static images, it would be nice to follow the development in time through animations The Paleomap Project homepage has many animations , but they do not work anymore, because they are using Java applets, which most browsers don’t accept nowadays. The site has not been updated since 2003 and I assumed that the project had been stopped. But searching information for this blog, I discovered that I was wrong, Scotese is still very active! But nowadays he and his coworkers create YouTube videos. Here is one of them. Time runs backwards, the video starts with the modern Earth and goes back to 750 million year ago.

It is also possible to predict how Earth will look like in the future. Of course such a prediction is less accurate because you have to extrapolate , using current plate movements.. Scotese’s prediction is that in the future another supercontinent will form, which he has called Pangaea Proxima. Here is the video. Notice that Australia will merge with Asia and l Antarctica.with India. The Mediterranean Sea will disappear.

Scotese’s YouTube Video Channel contains more than 70 videos about aspects of plate tectonics and continental drift. I will mention one more here, about the Story of the Malay Peninsula. (There doesn’t exist a Story of the Netherlands because God created the world, but the Dutch created The Netherlands 😉 )Notice how during the Ice Ages the sea-level was so low that the islands of the Malay archipelago were connected. This was called Sundaland. Topic for another post.

A few concluding remarks

  • Before Pangaea there have been several more supercontinents. Click here for a list.
  • When plate tectonics started on Earth, is still a matter of dispute. Possibly 3 billion year ago.
  • It can be argued that plate tectonics has been essential for the development of life. Watch this fascinating video The World before Plate Tectonics.

Beautiful Shapes

I could have named this blog Uniform Polyhedrons, but I think in that case not many would have read it 😉 A polyhedron is a 3D object, bounded by polygons and a polygon is a flat surface, boudned by straight lines. A cube is a simple polyhedron and a triangle is a simple polygon.MOre terminology in the appendix.

When I was a kid, I was fond of making cardboard models of buildings, ships etc. I bought the “bouwplaten” in the local bookstore. It was quite a popular pastime in those days, now no more. Here are two simple examples, found on the Internet.

It was during the 1970s , on a trip to London, that I came across the book Polyhedron models by Magnus Wenninger. It contained descriptions of 119 polyhedrons with detailed instructions how to make cardboard models of them. With my youthly love of bouwplaten and my interest in mathematics I immediately bought the book. Left my copy, right Magnus Wenninger (1919-2017) with a complicated polyhedron in his hands.

Back home, I bought sheets of colored cardboard and started building polyhedrons. Compared with the commercial “bouwplaten” as shown above, where you just have to cut out he various pieces, you have to draw the pieces first on the cardboard sheet, add tabs and then only cut them out. Here are two examples. The numbers are from Wenninger’s book, which can be found online.

The tetrahedron (left)is the most simple polyhedron, it consists of just four triangles. I have marked how many pieces you have to cut with a colored number. The football like polyhedron with the unspeakable name (right) consists of 30 squares, 20 hexagons and 12 decagons. 62 pieces in total.

Here are a few of the polyhedrons I have built. That was more than 40 years ago, the colors have faded. The polyhedron in the center of the top row is still “simple”, consisting of squares and triangles. The one left on the top row looks more complicated, but when you look carefully, you will see that it only consists of triangles! But only parts of a triangle are visible from the outside. In the right polyhedron, on the bottom row it is easy to see that there are pentagons (five-sided polygon), but there are also hexagons (six-sided polygons), which are hardly visible in this model. In total 12 pentagons and 10 hexagons!.

The polyhedrons where all faces are completely visible, are called convex, the others where you can only see parts of the faces are called nonconvex. See the appendix for more terminology and mathematical details.

Nonconvex polyhedrons are more difficult to build, because you have to be careful that the pieces of one polygon have the same color. But they are worth building, because they are beautiful. Here are a few examples. The left polyhedron consists of 12 pentagons and 12 pentagrams, 24 faces in total. The one at the right is more complicated , 20 triangles, 12 pentagrams and 12 decagons (10-sided polygon), total 44 faces.

Two more. The polyhedron left has 30 squares, 12 pentagons and 12 decagons, total 54 faces. And the beautiful polyhedron to the right has 20 triangles, 30 squares and 12 pentagrams, total 62 faces. The complexity of this polyhedron is difficult to see in a picture. On Wikipedia I found a 3D version which you can rotate with your mouse. Amazing, try it out and see if you can find the triangles (easy) and the squares (difficult).

The polyhedrons at the end of Wenninger’s book are even more complex, Here is a description with templates for the “Great Inverted Retrosnub Icosidodecahedron“. Yes, they all have names, see the appendix. It contains 80 triangles and 12 pentagrams, 92 faces in total .His description starts with “This polyhedron is truly remarkable in its complexity” and at the end he writes “Your patience and perseverance will have to hold out for more than 100 hours if you want a complete model of your own

At first I decided that “more than 100 hours” was too much for me. But I was curious about this polyhedron, and I used the templates to build a small part of it.. Soon I found out that there was something wrong with the templates for this model. Parts that had to be glued together, had different lengths! I tried to check and correct the size of the pieces (see right image with my comments) but that did not work..

I decided to contact Wenninger, but didn’t have his address, so I wrote to the Cambridge University press ( the publisher), asking them to forward my letter to Wenninger. I didn’t really expect a reply, so I was pleasantly surprised when after a couple of months I got a letter from Wenninger. He explained that in the printing process of the book one or two templates had been incorrectly represented. A few more buyers of the book had noticed the error. His letter contained the correct templates!.

After his kind gesture I felt “morally” obliged to build the polyhedron. I spent many evenings cutting and gluing the 1290(!) pieces. I did not keep track of the hours, but it must have been more than 100. Here is the final result. Of course I took a picture and sent it to Wenninger.

Here is a digital 3D version of the polyhedron. Rotate it with your mouse, to see the complexity.

I assume that in a reprint of the book the mistakes will have been corrected, but when I built the model, it must have been one of the few in the world ;-). Years later I visited the Science Museum in London, where they have the whole collection.

Polyhedrons have fascinated artists, philosophers and mathematicians throughout the ages. Here are Durer;s famous Melencolia I (1514) and John Cornu’s Melencolia (2011)

Appendix

First some terminology.

  • A polygon is a 2D figure with straight sides, for example a triangle. When all sides are equal it is called a regular polygon
  • A polyhedron is a 3D form bounded by polygons, for example a cube. A polyhedron has faces, edges and vertices (plural of vertex) When the polygons are regular and all vertices similar, the polyhedron is called uniform.

The left polyhedron has 6 faces (F=6), 12 edges (E=12) and 8 vertices (V=8). The right polyhedron has F=4, E=6 and V=4.

The most simple polyhedrons were already known in antiquity and are called Platonic solids. These polyhedrons have only one regular polygon as face. , a triangle, square or pentagon. Here they are

There are 13 polyhedrons that have more than more than one regular polygon as face.. They are called Archimedean solids, because they were first enumerated by Archimedes, later rediscovered by Kepler who gave them their names. Here they are. Notice that they all have one single edge.

The names give information about the composition of the polyhedron. For example the icosidodecahedron has 20 (icosi) triangles and 12 (dodeca) pentagons.

The polyhedrons often contain pentagrams. A pentagram is related to a pentagon by a process called stellation, extending the sides of a polygon. Polyhedrons can also be stellated by extending their faces. Left the pentagram and right one of the stellated dodecahedrons.(there are three more)

In the Platonic and Archimedean polyhedrons all faces are completely visible, The mathematical term is that these polyhedrons are convex. The stellated dodecahedron, shown above, has pentagrams as faces, but the center part of the pentagram is not visible, it is inside the polyhedron. The mathematical term is that this polyhedron is nonconvex. In total 53 nonconvex polyhedrons exist. This has been proven only in 1970.

Wenninger’s book describes 119 uniform polyhedrons, the 5 platonic solids, the 13 Archimedean ones, 48 polyhedron stellations and the 53 nonconvex polyhedrons. A List of Wenninger polyhedron models can be found on Wikipedia. The list contains images of all polyhedrons and lots of details

Here are the numbers of the polyhedrons shown in this blog (I have built more). 17, 24, 39, 76. 80, 99, 102, 105, 107 and 117.Except 39, a stellation of the icosahedron, they all have a Wikipedia page.

When I built my models, PC’s were still in an infant stage and the World Wide Web did not yet exist. Nowadays there is wealth of information available, there even exists software to create the polyhedrons digitally. Great Stella looks promising. I feel tempted 😉

Why did I write this blog, more than forty year later? Recently I visited the Bellevue Hotel in Penang. The owner of the hotel is a friend of mine. In the garden of the hotel he has built a geodesic dome. He was a close friend of the American architect and philosopher Buckminster Fuller (1895-1983), who was the “inventor” of the geodesic dome.

You will not be surprised that there is a close relation with the polyhedron models of Magnus Wenninger. Have a look at the Wikipedia article Geodesic polyhedron, where both Buckminster Fuller and Wenninger are mentioned. Enjoying the view and admiring the dome, the thought arose to write a blog about my “hobby” from the past 😉