Monday, July 25, 2011
There are three annoyances in space news today (and yesterday). They are:
This article on NASA's plans to send astronauts to a near-Earth asteroid. I don't see it as being as exciting as colonizing the moon (keep in mind that most people alive today have never experienced a manned mission there), but as something new and not too difficult it might be worth trying. However, the article says that:
The challenges are innumerable. Some old-timers are grousing about it, saying going back to the moon makes more sense. But many NASA brains are thrilled to have such an improbable assignment.
Ah. Wanting to colonize the moon certainly couldn't have anything to do with water and hydroxyl ever present in the soil and easy to find in the polar craters, the three-day journey time, lack of need to wait for launch windows to start a mission, or the fact that other nations are planning their own missions to the moon anyway. No, it's just old-timers grousing. Good to know.
The second annoyance is how many articles have been using recent close-up pictures of Vesta in stories about this planned near-Earth asteroid mission. One example can be seen here. While there are few out there more excited about Vesta than I am (I must have written about the approach phase a few dozen times over the past year), Vesta is about the farthest thing from the near-Earth asteroids NASA is looking at sending astronauts to. Consider:
- Vesta is in the asteroid belt in between Mars and Jupiter, near-Earth asteroids generally orbit around Earth to Mars
- Vesta has a diameter of 540 km or so, a mission-worthy near-Earth asteroid will probably be about 500 metres. That makes Vesta about ten billion times more massive.
- A mission on Vesta involves landing, a mission to a small near-Earth asteroid is more of a docking.
- Vesta is a formerly molten protoplanet, a near-Earth asteroid is likely to be dusty and rubbly. One of the challenges in exploring one would be the possibility of static electricity causing dust to clump and the slightest footprint stirring up a lot of it that the miniscule gravity would take a long time to settle.
So what would be a better photograph to use? 25143 Itokawa of course. 535 × 294 × 209 m in diameter, well-explored thanks to Japan, and in a similar orbit to some of the candidate near-Earth asteroids we are looking at. Itokawa looks like this:
It's actually so small that we could superimpose stick men and spacecraft on this image and imagine what they would look like while exploring. On this image one pixel is a bit more than one metre.
The last one is more of a Huffington Post groan than a true annoyance. Their article on the near-Earth asteroid mission is here, and it also has an image of Vesta. Even worse than the others though, the caption for the image is:
Eh, that's not Lutetia, nor does Lutetia resemble any of the near-Earth asteroids we're looking at either. Lutetia is actually quite big (that's why it's 21 Lutetia, the 21st to be discovered) but it's not Vesta big.
Lutetia was the largest asteroid we had encountered until Dawn approached Vesta. It's quite interesting, with a regolith some 600 m in depth and apparently some boulder tracks too. In terms of mass it's about 1/100 that of Vesta, so 100 million times more massive than 25143 Itokawa and the near-Earth asteroids NASA is looking at.