Friday, May 27, 2011
Interesting timing for these two stories from today and yesterday. Let's start with the asteroid mission. Yesterday NASA announced that they had chosen a sample-return mission to an asteroid out of three contenders. The other two were a sample-return mission to the moon, and a probe to the surface of Venus.
I'm actually glad that they didn't go with the Venus surface probe in spite of the fact that it is the planet I want to see properly explored the most, and that is because I don't want to see a surface mission that ends in a matter of hours; I want to see a solar flyer that stays in the clouds for months or years. Only then will we fully be able to drive the point home that the cloudtops of Venus are located in the most earthlike zone in the entire Solar System. A surface mission would only reinforce the idea that Venus is just a hellish planet that cannot be explored or colonized, that it's either orbit the planet in the depths of space, or brave the hellish surface. There is a moderate middle, and that probe would not have helped to show it.
Now to the asteroid probe: the asteroid is an interesting one, known as 1999 RQ36. Having flown close by the Earth before it has been well 'imaged' (by radar) by the Arecibo Observatory, so we know that it looks like this.
Not bad resolution for an asteroid just 560 metres in diameter.
The mission (OSIRIS-Rex) will first orbit the asteroid for a full year before doing a partial touchdown to grab some soil and then bring it back to Earth. This will be necessary to fully understand it and plan out well exactly where the sampling should take place. Apparently not spending long enough in orbit was the problem with Japan's probe to Itokawa.
...One day after that comes this news about water below the surface of the moon. We all remember the excitement over the discovery of water on the moon in the top soil, created by the solar wind interacting with the soil to create H2O and HO (hydroxyl). However, this only showed these two molecules to be present on the surface and did not tell anything about what lies below. Well, it turns out that the moon is actually as wet at the Earth below the surface. For how this was determined you should read the article yourself as I would just be repeating it if I summarized it here. The keyword there is: lunar melt inclusion. That's how we know about the water below the surface.