View Full Version : Looking at Jupiter, From Mars

2007-Feb-01, 01:52 AM
Guess who took this picture of Jupiter? Hubble? Keck? A well equipped amateur here on Earth? Nope, it was taken by the HiRISE camera on board the Mars Reconnaissance Orbiter. ...

Read the full blog entry (http://www.universetoday.com/2007/01/31/looking-at-jupiter-from-mars/)

2007-Feb-01, 02:24 PM
Question: What happened to the water of Mars? Stories say, Mars "lost" its water, but either it is still held in some form by the gravity of Mars or it drifted off into space. If the latter, could some molecules have found their way to Earth? When we look at our seas, are some molecules of Mars' water in it?

John Mendenhall
2007-Feb-01, 03:47 PM
There are several problems for water on Mars. And I'm going to write off the top of my head here, without digging out the references, so correct me if I'm wrong.

1. The atmosphere is thin. Only 1 millibar at the surface. It can't hold a lot of water, but, as I recall, it is saturated for the temperature and pressure on Mars. That is, the Martian atmosphere holds as much water as it can.

2. There is no UV blocking ozone layer. Ultraviolet light can easily dissociate water molecules into hydrogen and oxygen, and the hydrogen, being very light, is easily driven off by solar radiation pressure. The oxygen easily combines with iron, and we get the nice rust colored Mars.

3. There's not much gravity, I forget the figure, .6G or so. Certainly one of the terraforming Mars problems is finding a way to keep an atmosphere there.

4. There may be a lot of frozen water just under the surface. There is what looks like a dust covered frozen sea complete with ice floes, but until we get there and take a look, it's subject to interpretation.

In summary, Mars probably has enough water for our purposes, should we want to colonize. If Mars was a little larger and a little warmer, it sure would make a nice spare planet.

2007-Feb-01, 04:31 PM
The HiRISE camera uses the most powerful telescope every launched out of the Earth’s orbit.
^^typo ;)

Back on subject, quite an amazing picture

2007-Feb-01, 05:47 PM
Dang, that is a cool photo from Mars. I wonder when they will point that thing at Saturn? Amazing what that camera can do.....:dance:


2007-Feb-01, 09:27 PM
Would it really do much for Saturn?
I don't know how big the HiRISE telescope is, but there's certainly a compromise here. It's much smaller than Keck, but it's above the atmosphere, and at closest approaches its proportionally closer to Jupiter (~ 85% of Earth's distance?) than Keck. Looking at Saturn, it still has the no-atmosphere advantage, but it's not much different in distance (~ 95%?).
I suspect that small difference would not make up for its much smaller size. I would think Hubble's ACS, for example, should do far better -- if it hadn't just lost it!

Blue Fire
2007-Feb-02, 01:03 AM
From: http://uanews.org/cgi-bin/WebObjects/UANews.woa/4/wa/SRStoryDetails?ArticleID=10192

The largest science instrument on the spacecraft will be the University of Arizona's High Resolution Imaging Science Experiment (HiRISE), a 65 kilogram (145 pound) camera with a half-meter (20-inch) diameter primary mirror.My bold above, as to how big the instrument is.