Weblog
31 July 2018
Context map: NASA/Viking; THEMIS background: NASA/JPL-Caltech/Arizona State College; MARSIS knowledge: ESA/NASA/JPL/ASI/Univ. Rome; R. Orosei et al 2018
Astronomers have found water on Mars. We’ve heard this assertion a lot of time earlier than, usually with the breathless declare that the invention of Martian life would possibly quickly observe. So ought to this discovery increase our hopes for all times on Mars? Possibly, possibly not.
To start with, that is an fascinating discovery, and if confirmed it’s a doubtlessly large one. Our research of the Pink Planet has advised us that Mars was as soon as a heat, watery world. It had oceans of water in its early historical past. We additionally realize it’s early environment was wealthy with oxygen. So the situations of early Mars was very favorable to life as we all know it on Earth. However we additionally know that fashionable Mars is extraordinarily dry. There’s some water ice on the uncovered floor of Mars, however no lakes or oceans. There’s some proof of brine water beneath the floor, however not in massive portions. The floor of contemporary Mars just isn’t a spot the place life is prone to thrive.
Which brings us to this newest discovery. We’ve identified for some time that a lot of the Martian water is now frozen beneath the floor. There’s loads of water on Mars, simply not liquid water. One of many detectors on the Mars Categorical is MARSIS, which is a radar system that may bounce indicators off the Martian floor. The indicators penetrate the floor till they replicate off of one thing, sometimes water ice. By timing the arrival of the mirrored sign, we will map stuff beneath the floor. Whereas mapping Mars with MARSIS, the crew discovered a area close to the south pole that was a bit odd. It’s rather more reflective than different areas, which suggests it’s in all probability one thing completely different than the standard water ice. Liquid water is extra radar reflective than ice, so this appears to be like like water.
However we will’t bounce to conclusions. Earth has loads of subsurface water pockets, however Earth is geologically energetic and is comparatively heat beneath the floor. A lot heat for water to be liquid. However Mars isn’t geologically energetic, so it’s inside is chilly. On the depth of this specific area, the temperature is estimated to be virtually -70 levels Celsius. That’s far to chilly for liquid water, even when it’s beneath strain. However this reflective area can be on the backside of a layer of frozen ice, and that makes it appear to be a subglacial lake. We see this on Earth, the place water builds up beneath a glacier, even at temperatures effectively under zero. So it actually does appear to be liquid water. So what provides?
There’s a method to liquify water, even at -70 Celsius: make it actually, actually salty. We all know that there are numerous salts on Mars (perchlorates), and if these salts have been extremely dissolved in layers of subsurface ice, it might produce a area of briny liquid water, or maybe a slushy briny soup. So this is perhaps liquid water, however it must be actually salty. Much more salty than Earth’s oceans.
So what about life? On Earth, microorganisms have been present in very salty waters, such because the lifeless sea. However this potential Martian lake differs in two methods. For one, its rather more salty than the acute lakes of Earth. For one more, it’s extraordinarily chilly, with no clear supply of warmth. Even when there’s liquid water there, it’s not alternative for all times.
However we’ve been stunned earlier than. So if these area is confirmed to be a lake of liquid water it’s a robust discovery, and effectively price exploring additional.
