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  • How do you search for life on other planets? Follow the water!

  • Hi everyone, I’m Amy Teitel and I’m guest hosting for DNews. If youre among the living

  • you have something in common with every other life form on the planet: You need water to

  • live. So it would make sense that if you find the substance necessary for life on Earth

  • elsewhere, it increases the chances of finding extraterrestrial life. Now, weve never

  • found liquid water on Mars, so it’s probably not the best place to be looking, right? We

  • should be focussing our energies on the subsurface oceans on Titan and Europa, shouldn’t we?

  • Well, maybe not. A new study from a team at the University of Michigan has found a way

  • for liquid water to exist on the surface of Mars, and the key is salt.

  • Weve been exploring Mars with orbiters, landers, and rovers since the mid-1960s, and

  • most of what weve found where water is concerned is evidence that ancient Mars was

  • wet. Weve found weathered rocks indicative of ancient rivers, photographs of gullies

  • flowing down crater rims, and chemical signatures in rocks that can only have formed in the

  • presence of water.

  • But in 1998 we got an interesting break in the form of pictures from NASA’s Phoenix

  • lander. Some showed ice in trenches left by the lander’s scoop and others showed globules

  • on the landerslegs.

  • These globules caught scientistseyes because they not only persisted in later images, they

  • seemed to get bigger. It was a clear that something was happening on Mars. Could it

  • be that water droplets were somehow pooling on the lander’s legs?

  • The obvious problem in thinking the globules were water is Marsenvironment. Being further

  • from the Sun than the Earth with a much thinner atmosphere, the red planet is cold; the average

  • surface temperature is about 80 degrees below zero Fahrenheit.

  • This is where salt comes in. Just like how salt melts ice on the roads in the winter,

  • salt in Martian soil could melt subsurface ice.

  • It’s possible that the Phoenix lander blasted away enough top soil to expose the necessary

  • salts and subsurface ice for the two to interact and form liquid water, water that then froze

  • on the lander’s legs. Which means the same thing could be happening elsewhere on Mars

  • without the facilitating effects of a lander exposing the materials.

  • The key is the salt content in Marssoil. The Phoenix lander and the Curiosity rover

  • have both detected calcium perchlorate on Mars, a salty mixture of calcium, chlorine,

  • and oxygen that is also found in arid places on Earth like the Atacama Desert in Chile.

  • To test whether this salt could form water simply through contact with ice, the University

  • of Michigan team recreated Phoenix’s landing site and late spring/early summer environment

  • in a laboratory.

  • In one of these duplicate Mars environments the team put millimeter-thick layers of salt

  • on a temperature-controlled plate of Mars-like soil. And nothing happened.

  • But in the other duplicate Mars environment the team put calcium perchlorate directly

  • on a 3-millimeter-thick layer of ice and watched as drops of water formed within minutes, even

  • with the chamber set at minus 100 degrees Fahrenheit.

  • From these lab results the team concluded that small amounts of liquid water could exist

  • on Marssurface, specifically in shallow areas between the polar regions and mid-latitudes

  • during the daytime hours of the warmer spring and summer seasons. It’s a natural cycle

  • that might explain how gullies flow, freeze, and thaw before flowing again, and also might

  • explain how it is that water has been able to form just below the Martian surface. Which

  • might itself be a compelling way to look for life: weve seen frozen saltwater lattices

  • playing host to microbial life on Earth, so the same thing could be happening on Mars.

  • So do you think we should dig deeper into the Martian soil to see if there’s life

  • underneath? Tell us in the comments below and keep checking back here more DNews.

How do you search for life on other planets? Follow the water!

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B1 US lander water salt liquid water phoenix soil

How Salt Might Be The Key To Finding Life on Mars

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    羅紹桀 posted on 2015/08/02
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