Paintballing Apophis!

Before I started blogging, I wrote emails to a group of friends, interested in science. Several of these emails I have, after editing, entered as posts for my blog.
The first email (and now the first post on this blog) was about Apophis, an asteroid, that will pass Earth in 2029 at a close distance, and might (with a chance of 1 to 250.000) collide with Earth 7 years later, in 2036

This is an artist impression of Apophis, diameter ~ 270 m with an estimated mass of 27 megatonnes.

A collision with the earth would be a catastrophe. The impact would be the equivalent of 900 megaton TNT, ~ 60.000 Hiroshima atomic bombs.


When Apophis was discovered in 2004, there was a brief period of concern that this asteroid might hit Earth in 2029. It will not, and even in 2036 the chance is almost neglegible

But there are thousands of asteroids with orbits that may bring them close to Earth, so called NEA‘s, and NASA has an observation program to monitor them.

What to do when an asteroid is discovered which is on a crash course with Earth? We will have to deflect it! How? Many solutions have been proposed. Send a rocket to the asteroid and detonate a nuclear bomb, or let the rocket crash itself against the asteroid. Or use a strong laser beam to deflect the course.When you do this while the asteroid is still far away, a tiny change in course could be sufficient.

For a couple of years already a yearly competition “Move an Asteroid” is organised by the Space Generation Advisory Council , for students and young (space) professionals.

This year the competition was won by a MIT graduate student, Sung Wook Paek.

His winning proposal:

Launch a rocket, with a cargo of 5000 kg of pellets, filled with white paint. When near the asteroid, fire two salvos of pellets, timed in such a way, that the (spinning) asteroid will be completely covered with a very thin layer of white paint.

Here are two screenshots of a YouTube clip, published by MIT. In the left picture two pellet clouds are approaching the asteroid.  In the right picture one cloud has painted one half of the asteroid white already.

The colliding pellets will change the course of the asteroid a little bit. That is not new, but the white paint is. The photons from the sun will reflect against this bright white surface, and this results in (additional) radiation pressure. Also a tiny effect, so this kind of action should be taken, many years before the asteroid comes close to the earth.

Cosmic paintball, what a nice idea!

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