Name: 塩が火星の生命体を見つける鍵になるかもしれない方法 (How Salt Might Be The Key To Finding Life on Mars)
Uploaded: 2021-01-14T05:38:30.000Z
Duration: 3 min 15 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

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 you’re 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, we’ve 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.

We’ve been exploring Mars with orbiters, landers, and rovers since the mid-1960s, and

most of what we’ve found where water is concerned is evidence that ancient Mars was

wet. We’ve 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

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

These globules caught scientists’ eyes 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 Mars’ environment. 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 Mars’ soil. 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 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 Mars’ surface, 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: we’ve 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.