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September 2016 - Origin of Earth's H₂O
Report #19 - August 2016
Mars + Water?
Is Earth the only habitable planet in our solar system? Scientists have been scratching their chins and pondering this question for centuries. Backing up, we know that one necessity of life is water. It's old news that large amounts of water exist on Mars in the form of frozen rock-hard ice on its polar ice caps. Suspicious-looking gullies suggest possible liquid water, but "none have proved convincing." The mystery is finally over because, only recently, scientists were able to confirm liquid water on Mars, the fourth planet of our solar system.
This photo was false-colored to show the thin, dark brownish lines, or streaks, that run down Mars' terraneous surface; evidence of liquid water on the planet.
Taken by NASA's Lunar Reconnaissance Orbiter in 2011, channels imprint bold streaks on Mars' surface.
Before we get ahead of oursleves, it must be stressed that this "liquid water" on present-day Mars is only small amounts of damp soil, not "pools of standing water" like what could have been on Mars some billion years ago. Thanks to readings from orbit, waterlogged molecules were indentified by scientists in a paper published in the journal Nature Geoscience. These molecules are a specific kind of salt known as perchlorates, Found on Mars' surface, they were an instant indicator of water in the form of hydrated salts. This is due to the fact that, in order for hydrated salts to be produced, water had to have been present "recently," or over the span of a couple days. In 2011, "dark streaks" were discovered by one of NASA's high resolution cameras known as the Mars Reconnaissance Orbiter. These streaks, founded by Dr. McKwen and colleages, were located along Mars' crater slopes, canyons, ridges, and mountains. Over the summer, they would lengthen and fade under chilly temepratures, only to reappear the following year.
Through a time-lapse of the Palikir Crater, the behavior of the dark streaks overtime are animated as they bold in warm temperatures and fade as it becomes cooler.
Dark streaks 100 yards in length run down a slope in the Horowitz Crater.
These interesting streaks were named "recurring slope lineae," or R.S.L.s. If you were to pour water on concrete or dirt, the water would temporarily turn the surface a darker shade of what it was originally, only to evaporate and restore the concrete or dirt to its original color. Keeping this idea in find, some scientists believed water was to blame for Mars' streaks. Using a spectrometer, a device on the orbiter that identifies molecules based on the light they absorb, scientists were able to uncover signs of hydrated salt at four locations, which disappeared when the streaks faded. Mars' average temperature is -70 degrees Fahrenheit and approximately 70 degrees Fahrenheit at its equator. Liquid water is thought to remain on Mars' surface by the perchlorate salts lowering the freezing temperature.
Where's the Water Coming From?
That's a good question, and, unfortunately, it's one what still hasn't be answered yet. A basic rule of thumb is that water either comes from above or below. The following are a few theories that scientists have for the orgin of Mars' liquid water.
From Above?
Perhaps, just a like a sponge, moisture from the air is absorbed by the perchlorates. However, Mars has low humidity, allowing for only 1/2,500th (10 microns) of an inch of rain on its surface if all the planet's "wetness were wrung out of the air."
From Below?
Underground aquifiers could be the source of this water. Frozen during the winter, they melt in the summer, leaving a small amount of the aftermath of water to make its way to the surface.
Future R.S.L. Research
Nothing about R.S.L.s can be set in stone without further research. Unfortuantely, the idea of rovers investigating these potentially habitable areas up close poses too much of a risk due to the possibility of "contaminating" Mars with Earthern microbes that might have come with the equipment. Not only is it expensive to bake rovers at extreme temperatures to sterilize them of microbes, but such a design and heat resistant material would be just as costly and it's also simply a big price to pay if Martian life is jeopardized. NASA hasn't denied the idea of studying R.S.L.s into greater detail by potentionally detouring Curiousity, one of its rovers currently on Mars, to observe R.S.L.s, but officals have said that such an idea would "require debate and analysis."
Streaks along the walls of the Garni Crater are similar to those that run along a slope on the Horowitz Crater (above right).
SOURCES:
http://mobile.nytimes.com/2015/09/29/science/space/mars-life-liquid-water.html?referer=&_r=2
http://www.nytimes.com/interactive/2015/09/27/science/space/100000003943003.mobile.html?_r=0
Chang, Kenneth. "Mars Shows Signs of Having Flowing Water, Possible Niches for Life, NASA Says." Mars Shows Signs of Having Flowing Water, Possible Niches for Life, NASA Says. The New York Times, 28 Sept. 2015. Web. 24 Oct. 2015.
Images:
JET PROPULSION LABORATORY / UNIVERSITY OF ARIZONA, NASA
NASA / REUTERS