This Wednesday, a European landing craft called "Philae" will attempt humanity's first landing on a fast-moving comet (a complex chunk of ice approaching from the depths of space.)
After a 10-year, 4-billion mile journey to Comet Churyumov-Gerasimenko (C-G for short), the Rosetta spacecraft (which is now orbiting the comet) will drop a probe about the size of a kitchen range from a height of 13 miles. Taking some 7 hours to slowly land on its icy target, Philae will be moving at only 2 miles per hour at the end. Still, the gravity of the two-mile wide comet is so low, it could bounce off and move away or simply fall over and roll. To prevent this, the designers have equipped Philae with harpoons to grab the comet and with legs that have rotating screws in them to hold on to the ice for dear life.
Our robot representatives have only landed on six worlds so far: the Moon, Mars, Venus, Saturn's moon Titan, and two asteroids. None of those landings were quite as difficult and strange as this one. It takes radio signals from Rosetta about half an hour to get back to Earth even at the speed of light. Thus the European Space Agency controllers can't help Philae if it gets into trouble. Its own computer software will have to make the decisions that will lead to its survival or loss.
For a complete picture of Comet C-G, see my August 6 post. The photo accompanying today's post is a fantasy montage, showing the Philae lander safely on the comet's icy, boulder-strewn surface. The full comet has a weird L-shaped structure, as if two oval comets had somehow stuck together at a weird angle. Because its shape is so complex, its gravity is not simple either, making landing even more challenging. But if Philae lands, its 10 instruments will give us our first-ever up-close look at one of the chunks of ancient ice that are building blocks left over from the early days of our solar system.
Keep your fingers and toes crossed that the landing succeeds. For a basic animation of what the spacecraft will do and what instruments it carries, please see: http://www.youtube.com/watch?v=szKZ77MbF9Q
A fuller documentary about the Rosetta mission, see: http://www.youtube.com/watch?v=cArihDTnOZg
At the beginning of November, the Curiosity rover on Mars used a camera on its big arm to take this wonderful panoramic picture of itself and its surroundings. Dozens of individual pictures were stitched together carefully to make this self-portrait.
You can see four little trenches in the front where the arm scooped up some martian dirt for analysis.
Curiously, the way the images are taken and assembled, the arm is NOT visible in the picture. (You could imagine something similar if you held a camera out way in front of you and then took pictures from all sides. You could crop and assemble those pictures in a way so that your arm is always out of sight on the final image.)
In the background, on the upper right, you can see Mount Sharp, the mountain in the center of Gale Crater, which is the rover's ultimate destination. (See my blog post of August 19, 2012 for more on this mountain and its location.)
So far, all the instruments on board Curiosity are working fine, and the mission -- one of the most exciting astronomy events of the past year -- is continuing to send back good information from our red neighbor planet. As expected, we are already seeing clear evidence that there was lots of flowing water on Mars in the distant past.
P.S. If you are interested, you can see an animation of how this complex picture was taken and put together at:
http://www.nasa.gov/multimedia/videogallery/index.html?media_id=156880341
In view of the sudden importance that Big Bird and Sesame Street have assumed in the national presidential campaign, you may be amused that just recently, astronomers examining images of the battered surface of the planet Mercury have released this image of a large crater and several smaller ones that resemble "Cookie Monster."
Cookie Monster joins a set of craters on Mercury that resembles Mickey Mouse:
http://photojournal.jpl.nasa.gov/jpeg/PIA15862.jpg
and Miss Piggy on Venus:
http://photojournal.jpl.nasa.gov/jpeg/PIA00202.jpg
among the cartoon characters that fool our eye on other worlds.
Such images remind us of the flap, years ago, about the so-called "Face on Mars," which, in an early crude image, sort-of, maybe reminded some people of a face. Like the Cookie Monster on Mercury, it was a perfectly natural land form on Mars, which happened vaguely to resemble something familiar.
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