It seems I let the entire month of May and half of June go by without posting. The rovers have been roving, there were some glitches and reboots with a rover and with MRO, and Mars Express is into its third mission extension. Things seem to be going so well I guess we all get into a complacent mode with keeping track of what's happening.
The Mars Reconnaissance Orbiter had another reboot episode earlier this month and that's being looked into by the engineers. The HiRISE team has posted some new images including one of the so-called "cryptic region"—an area around the south pole that says very cold despite getting darker (indicating loss of ice/frost).
One interesting bit of work-in-progress comes from the Shallow Radar (SHARAD) instrument. It was designed to look for liquid water and as such has been studying gully features seen in parts of the Martian highlands. These features look like certain gullies on Earth that are formed due to the movement of underground liquid water. So far, no signs.
Opportunity, having done some amazing work leading to a better understanding of the water history of Mars, is now trucking its way along a 10 mile (16 km) path to the crater Endeavor—bigger than any crater it has looked at yet. In eight months of traveling, it is now about 1/5 of the way there.
Back in early May, Spirit got stuck in some particularly soft soil and the team is working on a solution. As part of this effort, they even used the microscopic imager to look underneath the rover itself. It's an interesting picture made more so since this is not how this camera was ever intended to be used. Engineers are a very resourceful lot!
If you haven't already downloaded and spent hours flying around the globe using Google Earth, well, I highly recommend it. It's an advanced version of their web-based mapping software.
Quite some time ago, Google Maps added in some astronomical maps. You can use the web-based server to look at the Moon or Mars. A short time ago, Google took these 2-d Mars maps and married them to their 3-d Google Earth program along with all the 3-d (topography) data. The results is a desktop application that runs under all three of the major operating systems (Linux, MacOS X, and MS Windows).
Now most of this falls into the category of Old News but what got me thinking of it again was this blog post that points out some of the finer points and little-known-features of Mars in Google Earth. The one I found the most fun is the Rover Tracks—you can follow both Spirit and Opportunity on their entire journeys from start to (almost) where they are right now.
Download, install, and have fun!
Right now Mars is well into its northern autumn or southern spring. This means that, due to the tilt of Mars (about the same as Earth's), the southern pole is beginning to be pointed more directly towards the Sun. The increasing sunlight leads to increasing temperatures both on the ground and in the atmosphere. It also turns out that as the south moves into summer, the heating is even greater than it is in the north since Mars is about 35 million miles closer to the Sun (Earth's orbit varies by only about 5 million miles).
The heating and pressure difference during southern summer can loft dust up into the air. This dust can heat up very quickly during the day but it also cools quickly overnight. So if there is an increasing amount of dust in the air, we would expect to see more summer heating in the daytime atmosphere than in the night time atmosphere.
Well, the Mars Climate Sounder aboard the Mars Reconnaissance Orbiter is seeing just that. The MCS measures the amount of infrared light emitted by the martian atmosphere by looking at the limb of the planet—so the background is just cold, dark, space.
You can check out the changing MCS measurements over the last few days and see the images at the team blog site noted above.
A fellow MarsWatch'er pointed me to notices of some very interesting work that has been presented at the 40th Annual Lunar and Planetary Science Conference (I don't usually go to this meeting and had not yet gone over the abstracts). The work itself was presented on 23 March and reported on rather quickly by friend-of-planetary-science Kelly Beatty at Sky & Telescope.
It appears that some photos of the leg strut of the Mars Phoenix lander showed what appear liquid drops clinging to it. What makes this so amazing is that water on Mars simply can not exist in the liquid phase. Why is that? It's due primarily to the atmospheric pressure. For example, if you put water into a pot and seal a lid on it, you can heat that water far above the standard boiling point, and thus cook food faster—that how a pressure cooker works in your kitchen. On the other side, those who have lived at altitude know that water boils at a lower than normal temperature. Back when I was in Laramie, Wyoming we used to have fun watching students' faces when they measured the boiling temperature in the lab. It never reached 100°C but instead boiled in the low 90's. This is one reason for "high altitude" baking directions.
The lower boiling point is because there is less air pressure above the liquid making it easier for individual water molecules to leave the liquid surface. It also depends on the local humidity, but that is temperature and pressure dependent as well. So now if we go to Mars where the air pressure is about 1% that of Earth, it is very easy for water molecules to leave a liquid surface; in fact, individual molecules can easily leave a solid surface so the ice will simply sublime away. You can see this effect in your own freezer if you leave ice cubes in there for a long period of time—they decrease in size but never leave behind a puddle of liquid.
So how can we have a picture of liquid water on Mars? The key is salts. Those living in northern climates know that adding salt to ice lowers its melting point. This means that it can be liquid at colder temperatures and your sidewalk won't be icy. Salts also increase the boiling point so that you can have liquid at higher temperatures.
Combine the pressure and salt effects and, according to Nilton Renno and his collaborators you can get liquid brine on Mars. You can see a summary of his work, and some pictures, at this page at the University of Michigan where he does his work.
Of course, the most interesting point of this is that liquid water appears to be the most important ingredient of life. And now we have it on Mars.
A while back I received notice that some images from our site had gone missing. It turned out to be far more severe than that—all of the 2007/8 images had gone missing. Seems some hack-bot script had hijacked my space on the server and in the process, deleted all the images. And me without an archival backup!
I sent out a message to all contributors to ask for resubmission and the first reply I got back, from Ljubomir Djurisic, said that he had done an entire archive of the images up through about mid-June 2008. This recovery saved me a lot work so my thanks go out to Ljubomir.
For the images that came in after that, I have been able to contact those observers and have also recovered those—thanks to them for helping!
I think the archive is good now; the problem is fixed and we should be fine going forward. Just a note to the concerned: the hack was not anything that could affect visitors to the site, that is, no viruses were planted for spreading so you have nothing to fear for uploads during the next apparition.