Category Archives: Mars

Sweatin’ Mars

Liquid Saltwater Likely Present on Mars

What happens when you have salt water on a surface in cold weather?  On a human body, it comes out of pores as sweat and if the conditions are right, it condenses on the skin as droplets of salty water.  The saltiness means that they probably wouldn’t freeze to your skin until it gets very, very cold — which is why if you exercise outside in the winter, sweat droplets don’t turn into ice blobs right away, even if they land somewhere other than on your warm skin.

Droplets of salty water on the legs of the Mars Phoenix Lander. (Click to emibiggen.)
Droplets of salty water on the legs of the Mars Phoenix Lander. (Click to embiggen.)

It turns out that this tendency of salt water to freeze more slowly in cold weather is behind the discovery of water droplets on the legs of the Mars Phoenix Lander which is sitting silent in the Martian north polar region.

Scientists at the University of Michigan have analyzed an an image taken during the mission and say that this is proof of liquid water on Mars.  This is the first time liquid water has been detected and photographed anywhere but Earth.

So, how could this be?

The common wisdom is that water exists on Mars only as ice or vapor. This is because of the planet’s low temperature and atmospheric pressure. Any water ice that did get exposed would probably vaporize in the low pressure and dry conditions, but it wasn’t likely to just simply melt.  At least, that was the thinking before the Mars Phoenix mission landed.

It came to rest in a place where an interesting confluence of conditions exist to make the droplets of salt water found on the Phoenix lander leg possible. First, temperature fluctuation in the arctic region of Mars where Phoenix landed and salts in the soil could create pockets of water too salty to freeze in the climate of the landing site.

The droplets you see on the leg in the image grew during the polar summer. Based on the temperature of the leg and the presence of large amounts of “perchlorate” salts detected in the soil, scientists think that the droplets were most likely salty liquid water and mud that splashed on the spacecraft when it touched down. The lander was guided down by rockets whose exhaust melted the top layer of ice below a thin sheet of soil.

Some of the mud droplets that splashed on the lander’s leg appear to have grown by absorbing water from the atmosphere, Images suggest that some of the droplets darkened, then moved and merged—physical evidence that they were liquid.

So, where did the salt water come from?  The wet chemistry lab on Phoenix found evidence of perchlorate salts, which likely include magnesium and calcium perchlorate hydrates. Mix these with water vapor released during landing and you have compounds with freezing temperatures of about -90 and -105 Fahrenheit respectively. The temperature at the landing site ranged from approximately -5 to -140 Fahrenheit, with a median temperature around -75 Fahrenheit. Temperatures at the landing site were mostly warmer than this during the first months of the mission.

The Michigan team did thermodynamic calculations, which provide additional evidence that salty liquid water can exist where Phoenix landed and — this is important — elsewhere on Mars.And the fact that the droplets seem to grow as time went by implies more salty water available than the amount melted when the lander came to rest on the surface.

Now, this is quite interesting of course because water is one of those things that we’re pretty sure that life needs to survive in the long term. And, we know that life can exist in pretty salty environments (the so-called halophiles). So, the discovery that liquid salty water can exist on Mars is a big boost for the search for places where life could exist on Mars (now or in the present).  Looking at it another way, knowing that such conditions exist on Mars widens the number of places where we know conditions are suitable for life.

Stunning Dunes on Mars

Surrealist Scene on the Red Planet

I was going to write about the Brian the Bat today, and his apparently untimely demise during the launch of Space Shuttle Discovery a few days ago, but I see that Ian O’Neill over at Universe Today has covered it nicely, so go check it out. Instead, I’m going to give you another gorgeous scene from our favorite planet (at least here at the Rambling Hacienda)–Mars. This one is absolutely stunning in its detail — a set of dunes in Proctor Crater in the southern hemisphere of the planet. Click on it to get the big view and just feast your eyes. Then come back here for a discussion of it.

Sand dunes and ripples in Proctor Crater on Mars. Courtesy Mars Reconnaissance Orbiter. (Click to embiggen.)
Sand dunes and ripples in Proctor Crater on Mars. Courtesy Mars Reconnaissance Orbiter. (Click to embiggen.)

This view was snapped by the High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter, and it shows what geologists call aeolian bedforms.  The term aeolian is used to indicate “wind-blown” materials that were blown across the surface and deposited in features like these dunes and ripples.

On this image, the relatively small ridges are ripples made up of very fine sand mixed with a bit of larger sand bits and granules of rock. The larger dunes are made of sand as well and they move faster across the surface than the ripples do. All of the material you see here is made of rocks that once flowed from volcanoes (known as basaltic lavas).

What I really find very cool is to study the large version of this image (which you can get to by clicking on this smaller one — it may take a bit to open — it’s big). Do that and you can see even finer ripples in the dark areas and ripples within ripples within ripples in the brighter areas. It’s just amazing detail and I want to be there digging into the sand with my geologist’s shovel and taking samples!!