07-25-2018, 05:44 PM
(This post was last modified: 07-25-2018, 07:41 PM by infinitempg.)
So as some of you might know I'm currently in graduate school for astrophysics, and one of the important parts of doing that is being able to explain space-stuff™ to non-academics. With the news today about possible Mars water, I figured I'd practice my science communication skills by subjecting a bunch of football fans to astronomy. If this actually takes off maybe I'll do more as new interesting things happen! Anyways, on to the show:
[div align=\\\"center\\\"]spaceNEWS
by Micycle McCormick[/div]
Astronomers Find Possible Evidence for Liquid Water on Mars
Researchers in Italy (Orosei et al.) announced today in Science (linked at the bottom of this article) that they have found evidence of a "stable body of liquid water" on Mars. This water appears to be in the form of a lake approximately 20 km wide and placed 1.5 km below the ice sheets located on the Martian south pole. Because of the high amounts of perchlorates and and alkaline metals (which come together to make salts), it's expected that the water is extremely salty. This is a good thing, as salt dissolved in water helps lower the freezing point of the said water, in this case down below the expected temperature at the base of the lake of 205 K (-68.15°C/-90.67°F). (For reference, that's a 68 K/68°C difference from the freezing point of pure water.)
How did they find this?
The researchers utilized a technique known as Radio Echo Sounding (RES), which is essentially radar. The transmitter will send down a low frequency radio wave to the surface of the object (in this case Mars) and time how long it takes for it to bounce/reflect back, helping them determine shape, size, and relative velocity. The reflection is caused by highly conductive objects, such as metals and seawater. Ice, on the other hand, is not extremely conductive at these frequencies, and at certain frequencies, can be easily penetrated through by radio waves.
The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS, because politicians aren't the only ones who have fun with initialisms) instrument on the European Space Agency's Mars Express orbiter is an ice-penetrating radar capable of working through glaciers such as the ones on the Martian South Pole. Using this instrument, the researchers measured the strength of the reflected signal to determine the relative dielectric permittivity - which to put extremely simply is a measure of how much of the signal can pass through (high permittivity means more signal returns). Different materials have different permittivities, and in this case they found values in the region similar to liquid water on Earth.
[div align=\\\"center\\\"]![[Image: F3.large.jpg]](https://d2ufo47lrtsv5s.cloudfront.net/content/sci/early/2018/07/24/science.aar7268/F3.large.jpg)
[/div]
If you look at Fig. B in this image, you can see outlined in black an extremely blue portion of the map. This is a map of the "normalized basal power", or the strength of the returning signal (dB is a measure of intensity). Looking at the colorbar on the right, we see that this extremely blue area is a sure signal of high intensity, matching what we know about liquid water - high permittivity, leading to a large amount of the signal returning to the radar.
What makes this different from before?
This is arguably the first time that anyone has detected stable, liquid water on Mars that doesn't disappear. The polar ice caps are mostly frozen water (i.e. ice), the glaciers are also ice, and there is some evidence of permafrost-like features beneath the surface. There was a claim of seasonal flows of water on Mars in 2011, where it was believed that liquid water created streaks on the surface before disappearing because of the low temperature and pressure. However, this was just recently proven incorrect by the Mars Odyssey orbiter, which found no evidence of water in the studied areas. This discovery, however, is stable, liquid, and isn't going anywhere anytime soon.
We do need to be careful about taking this as fact. MARSIS does not have very good spatial resolution, and as a result isn't perfect at determining the difference between water and salty dirt. MARSIS's brother, the Mars SHAllow RADar sounder (SHARAD, see what I mean) on NASA's Mars Reconnaissance Orbiter was unable to find any evidence of liquid water, although it operates at slightly higher frequencies and thus is unable to penetrate through as much ice as MARSIS is.
What implications does this have?
On life? Who knows. The rule has always been to follow the water, as water is the only way for life as we know it to survive. The presence of liquid water on Mars doesn't mean life is there, but it gives us somewhere to look for life. A concern I have on the top of my head is how life would be generated from not life, as some sort of energy is needed to enter the system. We don't know if there are any hydrothermal vents located in this area, or in any other possible subglacial lake, and there certainly isn't going to be any lightning striking the water.
This water is also in a pretty poor place for potential Martian colonists, as it's over a kilometer below the ice cap's surface. It may even be more advisable that humans go nowhere near this site as to avoid contamination and allowing Earth life to utterly destroy anything that might be there. (We could probably send machines, though.)
One impact this discovery might have is producing another orbiter capable of penetrating the ice with better resolution. We know this technology works extremely well, as we've tested it on Earth (sidenote: this is yet another reason why the federal government shouldn't cut NASA's Earth Science funds but that's a political rant for another time), but haven't gotten any more up to Mars. The Mars Reconnaissance Orbiter arrived at Mars in 2006, and the Mars Express arrived in 2003 - that's over 12 years without new technology. Many planetary scientists have been begging for a new one to be sent, and this discovery might inspire a change in fund appropriation.
[div align=\\\"center\\\"]- LINK TO THE PAPER -
[/div]
(it appears to be publicly available but if not then I can't really share the document with you due to weird restrictions - if it's unavailable try to find a college campus or something)
TL;DR: There might be water on Mars, as detected by ice-penetrating radar. We're not actually sure if it's there (and we don't have the tech to adequately confirm this), but all the evidence we have points to this being the logical conclusion. Also it's not going to be super helpful if we colonize.
I'd love to try to answer any questions anyone might have, and take any criticisms of the format. I'm worried that I may be making this too complicated, so I would really like to know if I need to make things more simplified the next time around.
[div align=\\\"center\\\"]spaceNEWS
by Micycle McCormick[/div]
Astronomers Find Possible Evidence for Liquid Water on Mars
Researchers in Italy (Orosei et al.) announced today in Science (linked at the bottom of this article) that they have found evidence of a "stable body of liquid water" on Mars. This water appears to be in the form of a lake approximately 20 km wide and placed 1.5 km below the ice sheets located on the Martian south pole. Because of the high amounts of perchlorates and and alkaline metals (which come together to make salts), it's expected that the water is extremely salty. This is a good thing, as salt dissolved in water helps lower the freezing point of the said water, in this case down below the expected temperature at the base of the lake of 205 K (-68.15°C/-90.67°F). (For reference, that's a 68 K/68°C difference from the freezing point of pure water.)
How did they find this?
The researchers utilized a technique known as Radio Echo Sounding (RES), which is essentially radar. The transmitter will send down a low frequency radio wave to the surface of the object (in this case Mars) and time how long it takes for it to bounce/reflect back, helping them determine shape, size, and relative velocity. The reflection is caused by highly conductive objects, such as metals and seawater. Ice, on the other hand, is not extremely conductive at these frequencies, and at certain frequencies, can be easily penetrated through by radio waves.
The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS, because politicians aren't the only ones who have fun with initialisms) instrument on the European Space Agency's Mars Express orbiter is an ice-penetrating radar capable of working through glaciers such as the ones on the Martian South Pole. Using this instrument, the researchers measured the strength of the reflected signal to determine the relative dielectric permittivity - which to put extremely simply is a measure of how much of the signal can pass through (high permittivity means more signal returns). Different materials have different permittivities, and in this case they found values in the region similar to liquid water on Earth.
[div align=\\\"center\\\"]
[/div]If you look at Fig. B in this image, you can see outlined in black an extremely blue portion of the map. This is a map of the "normalized basal power", or the strength of the returning signal (dB is a measure of intensity). Looking at the colorbar on the right, we see that this extremely blue area is a sure signal of high intensity, matching what we know about liquid water - high permittivity, leading to a large amount of the signal returning to the radar.
What makes this different from before?
This is arguably the first time that anyone has detected stable, liquid water on Mars that doesn't disappear. The polar ice caps are mostly frozen water (i.e. ice), the glaciers are also ice, and there is some evidence of permafrost-like features beneath the surface. There was a claim of seasonal flows of water on Mars in 2011, where it was believed that liquid water created streaks on the surface before disappearing because of the low temperature and pressure. However, this was just recently proven incorrect by the Mars Odyssey orbiter, which found no evidence of water in the studied areas. This discovery, however, is stable, liquid, and isn't going anywhere anytime soon.
We do need to be careful about taking this as fact. MARSIS does not have very good spatial resolution, and as a result isn't perfect at determining the difference between water and salty dirt. MARSIS's brother, the Mars SHAllow RADar sounder (SHARAD, see what I mean) on NASA's Mars Reconnaissance Orbiter was unable to find any evidence of liquid water, although it operates at slightly higher frequencies and thus is unable to penetrate through as much ice as MARSIS is.
What implications does this have?
On life? Who knows. The rule has always been to follow the water, as water is the only way for life as we know it to survive. The presence of liquid water on Mars doesn't mean life is there, but it gives us somewhere to look for life. A concern I have on the top of my head is how life would be generated from not life, as some sort of energy is needed to enter the system. We don't know if there are any hydrothermal vents located in this area, or in any other possible subglacial lake, and there certainly isn't going to be any lightning striking the water.
This water is also in a pretty poor place for potential Martian colonists, as it's over a kilometer below the ice cap's surface. It may even be more advisable that humans go nowhere near this site as to avoid contamination and allowing Earth life to utterly destroy anything that might be there. (We could probably send machines, though.)
One impact this discovery might have is producing another orbiter capable of penetrating the ice with better resolution. We know this technology works extremely well, as we've tested it on Earth (sidenote: this is yet another reason why the federal government shouldn't cut NASA's Earth Science funds but that's a political rant for another time), but haven't gotten any more up to Mars. The Mars Reconnaissance Orbiter arrived at Mars in 2006, and the Mars Express arrived in 2003 - that's over 12 years without new technology. Many planetary scientists have been begging for a new one to be sent, and this discovery might inspire a change in fund appropriation.
[div align=\\\"center\\\"]- LINK TO THE PAPER -
[/div]
(it appears to be publicly available but if not then I can't really share the document with you due to weird restrictions - if it's unavailable try to find a college campus or something)
TL;DR: There might be water on Mars, as detected by ice-penetrating radar. We're not actually sure if it's there (and we don't have the tech to adequately confirm this), but all the evidence we have points to this being the logical conclusion. Also it's not going to be super helpful if we colonize.
I'd love to try to answer any questions anyone might have, and take any criticisms of the format. I'm worried that I may be making this too complicated, so I would really like to know if I need to make things more simplified the next time around.
![[Image: 55457_s.gif]](https://signavatar.com/55457_s.gif)
Eleven Kendrick-Watts, #13 WR ![[Image: 54619_s.png]](https://signavatar.com/54619_s.png)
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