Mars Phoenix Finds Ice on Mars - Some Cool Info

21 Jun 2008

Mars Rover

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Since NASA reported that the Mars Rover found ice on Mars yesterday, I figured I’d spread the word about the finding and some cool ways to keep up with the latest information. First of all, a cool widget showing the current Mars weather information:

You can also check out the Mars Rover Twitter feed: Mars Rover on Twitter

Here is some cool information from a story on Wired.Com:

How do you know it’s water ice, not CO2 ice (aka ‘dry ice’)?

There is a lot of CO2 ice on Mars in the winter. However, Phoenix landed in the Martian arctic during the summer (because the lander is solar powered, the extra summer light is a necessity). In the Martian summer it is much too hot for dry ice to be solid. It would be like trying to keep water ice from melting on a 140-degree day here on Earth.

Carbon dioxide (CO2) will freeze on Mars at -125 C. Today’s weather report from the Canadian weather station on Phoenix shows a low of -80 C — way too hot for dry ice to stay solid right now. (Note the largest “pebbles” of ice were seen to stay solid for a day before disappearing).

Why not send instruments to detect life?

If you are going to make a claim like, “I have found life on Mars,” you have to be prepared to show that there is NO chance your sample was contaminated with Earth bacteria before launch. To do that takes an incredible amount of sterilization. Don’t worry — they have already done a lot of sterilizing on the Mars Phoenix before launching it. But to really be sure they would have to go to extreme measures to be able to rule out any contamination, and doing that would have drastically increased the cost of the mission beyond its budget. So NASA and JPL plan missions that look for water and the conditions of life within the budgets they have now.

What about the bright white stuff in the sunshine?

The scientists said they are monitoring the bright patches in the sunshine for changes too. They are seeing some changes, but stay tuned for more explanation and details. As for how the “pebbles” that disappeared did so in the shade, one scientist did mention that the portion of the trench it was in was exposed to morning sunshine earlier in the day.

Why are the pictures not all in color?

Be patient. The first images sent out are the raw files from the lander. The science team is committed to getting us the images to us fresh off the presses, so they send out the raw (monochrome) images first. Typically if you wait a day, the team will release the image in full color once it has been processed (see above for full color version of yesterday’s image).

How can water ice go straight from being a solid to being a gas (sublimation)?

Just like dry ice does here on Earth, water ice goes from solid to gas when the pressure is below 6.1 millibars and it gets heated (like it does in the Martian sun). It can also go straight from solid to gas above 6.1 millibars when the vapor pressure (amount of water vapor in the air) is low enough. This is because the molecules of water in solid form and gas form are not at equilibrium.

You might be surprised to know that the same thing happens here on Earth. If you have a frost-free freezer, you may have noticed that your ice cubes gradually shrink over a period of days. This is sublimation: the fan is constantly sucking water vapor out of the freezer so the ice cubes surrender more and more water molecules to the dry air over time.

The pressure on Mars is about 8 millibars, very close to the “triple point” of water, which is the point where it can easily exist as either a solid, a liquid or a gas (see the chart below). Since the vapor pressure is so low, water can easily sublime in the Martian atmosphere, especially as the surface heats up in the sunshine. When that happens, the soil can often get hotter than the air in the sunshine (think of a lizard sunbathing on a hot rock).