Water Found on Mars! (Once more.)

By Grace Bischof

Just lately, fellow PVL member Charissa Campbell was concerned in a JPL press launch detailing the Martian clouds she captured in her Cloud Altitude Statement. The photographs consisted of gorgeous clouds drifting throughout the Martian sky, doubtless composed of CO2-ice on account of their excessive altitude within the ambiance. I spent a while studying the replies to the press launch on social media, lots of which pose questions in regards to the composition of the clouds on Mars. “Clouds means water?” writes one of many commenters. In the meantime, “What are the clouds manufactured from? [because] there ain’t no water vapour floating round on Mars, proper?” inquires one other.  

Properly, I’ve some excellent news for everybody: there’s water on Mars! However earlier than you name your native newspaper to report the thrilling revelation, I’ve some explaining to do. The presence of water on Mars has been confirmed for the reason that late Sixties, when water vapour traces had been detected in spectra of Mars noticed with an Earth-based telescope. Since then, water has been “found” on Mars over and again and again (see: any Day by day Mail article about Martian water). So, let’s clear this up. Water exists on Mars in each vapour and ice type. The confusion arises after we think about the best way we discuss water in day-to-day life. In common dialog, we are saying “water” after we imply liquid H2O, and “ice” after we imply strong H2O. This verbiage doesn’t maintain in planetary science settings as a result of “ice” to refers to any strong type of a condensable species: for instance, CO2-ice or H2O-ice. Due to this confusion, the shortage of liquid water leaves folks believing there isn’t any water in any way.

So, let’s take a better have a look at the water on Mars. Mars’ ambiance is way thinner and has a lot much less water vapour than Earth’s ambiance. Nevertheless, the quantity of water vapour is enough to condense to type water-ice clouds within the ambiance. Every Mars Yr, when the planet is at its aphelion place (the furthest level from the solar) a belt of water-ice clouds varieties within the equatorial area of the planet, known as the Aphelion Cloud Belt. These clouds have been noticed by orbiters round Mars and cameras on the floor, notably by the Curiosity rover. Water-ice clouds exist in different areas, as nicely, reminiscent of within the Martian Arctic. The Phoenix mission captures photos of fluffy clouds drifting previous its touchdown website throughout the second half of the mission. The Floor Stereo Imager and lidar onboard the lander had been used collectively to seek out proof of water-ice fog close to the floor of the lander. The Phoenix mission was additionally the primary mission to seize precipitation (snow) falling from the clouds.

The opposite frequent place to seek out water on Mars is as water-ice within the subsurface. The Phoenix lander was outfitted with a robotic arm to dig into the Martian soil. They had been capable of finding ice within the space across the lander at many depths, ranging all the way down to 14 cm. At each the north and south poles you’ll find a big polar cap primarily composed of water-ice coated by a layer of CO2-ice. Areas of the south polar cap resemble Swiss Cheese, the place pits within the CO2-ice layer expose water-ice beneath. PVL member, Alex Innanen, has examined the Swiss Cheese pits to find out if the water vapour sublimated from the Swiss Cheese contributes considerably to the general world water vapour abundance. 

So, what about that coveted liquid water? Properly, it’s sophisticated. Presently, no our bodies of liquid water can exist on the floor of Mars. The ambiance is so skinny that uncovered water-ice sublimates straight to water vapour when heated and deposits again to ice when cooled. Geomorphic proof, reminiscent of river deltas, present us that Mars had liquid water on the floor in its previous. In 2018, radar evaluation of Mars’ south pole noticed proof of a subsurface liquid-water lake. It was theorized the lakes could be extraordinarily salty, bringing the freezing temperature down and permitting the water to remain liquid. In 2021, a York U professor, Dr. Isaac Smith, launched a paper explaining that the radar observations are higher described by hydrated and chilly clay-rich deposits (https://doi.org/10.1029/2021GL093618), relatively than salty lakes. 

Liquid water on Mars is an thrilling notion as a result of it results in many questions on the habitability of the planet, each previous and current. However liquid water just isn’t the one fascinating section of water – it’s clear we actually love the clouds right here at PVL. Nonetheless, if liquid water is ever discovered, you may positive count on to see a daring headline declaring “Water Found on Mars!”, during which case, you may refer again to this weblog submit.