‘Back on March 10, the Mars Reconnaissance Orbiter successfully entered orbit around Mars (so it could do reconnaissance). Once the orbit was established, scientists and engineers needed to make sure everything was okay before turning on the cameras, but finally on March 24 they got their first image. Here it is!
Actually, this is only a tiny piece of the full image. This image shows an area of Mars about 1.5 x 1.5 kilometers on a side. The full image is 50 x 23.6 kilometers (and would be 20,000 x 9500 pixels in size, so forgive me for not displaying it here). The image displayed above is actually resized, so it’s not at full resolution– click it to see the highest res version of the image.
There’s lots of cool stuff to see. It looks to me (but I’m not an expert) like that gully has had multiple episodes of flooding of some liquid (water? lava? clathrates?), or either freezing or evaporating to leave that step-like structure. You can see lots of craters too.
It’s always hard to tell when looking at Mars what scale you’re seeing. Craters come in all sizes, and the weird features look too weird to guess at their size. In this case, we know that the scale of this image about 2.5 meters per pixel. It’s hard to see the pixels in that image, so the scale is still hard to see. Let’s zoom in on the medium-sized crater in the lower left and see if that helps.
You can see the pixels pretty well now. I measure the crater as being about 12 pixels across, making it 12 x 2.5 = 30 meters across.
OK, read that again: 30 meters across. That’s small. Positively tiny. I’m used to thinking of craters being kilometers across, but this one is smaller than a football field! In fact, take a look at this picture:
This is a satellite image from Google Earth of a baseball field not too far from my house. You can see cars lining the streets to the east, to give you a sense of scale. That image is at the same scale as the crater image above. Comparing them, you can see that the crater would pretty much fit in the infield (the circular wedge lined with dirt) of the baseball field.
Look at that again. A decent runner could stand on the edge of the rim of the crater and run straight across it in just a few seconds. Geez, I could. That’s how small that crater is. Each pixel is about the size of a car.
May I remind you that that crater is on Mars? You know, the planet, the one really far away?
Wow. The camera that took this image — called HiRISE, for the High Resolution Imaging Science Experiment camera — is the most powerful ever flown to Mars. But this gets better: MRO is still in a highly elliptical orbit. Engineers are slowly lowering the spacecraft (by repeatedly dipping it into Mars’s atmosphere!) to put it in a "mapping orbit". So in a few months the orbit will drop enough that the camera will be able to take images at a resolution of 28 centimeters per pixel. That means that if those cars were on Mars, MRO would be able to see people in them. 30 cm is about the size of a human head, more or less, depending on the head.
Wow again. I can’t wait to see pictures at that scale. What will they reveal? The rovers have done a magnificent job, but Mars is big and they’re slow: we only have super-high-resolution images of a very small fraction of Mars. MRO and HiRISE together will map a large portion of Mars with incredible detail– even better than you can get with Google Earth. Will there come a day when we have another planet mapped better than we do our own?
Maybe when that day comes, Earth won’t be referred to as “our own” any more. I think we may just have to include other planets in that list.’
April 2nd, 2006 at 2:06 pm
Another test