It will be a good day for the spring of Poland, when Mars is finally colonized: the only option for bottling, when you live on a planet whose last substantial traces of liquid liquid water disappeared a few billion years ago. That ancient water has caused much study and debate, and has provided the name of at least one Franco-Candian psychological rock band. The fact that it existed, at a given time, is a big part of why the dreams of annexing Mars have flourished. But where exactly was it? Why majestic geological processes disappear the mbadive bodies of space-liquid? For this week's Giz questions, we spoke with several Mars experts to find out.
Professor of Geosciences, Virginia Tech, who studies the formation and evolution of planets.
There is a series of lines of evidence that at some time in the past there was more water on the surface of Mars compared to the cold desert conditions we observe today. Where this water was one of the great puzzles of our solar system.
As a geophysicist who spends a lot of time thinking about subduction zones on Earth, I am more surprised than most people by the disappearance of water from the surface of Mars. This is the why. On Earth, water reacts with rocks in and below the ocean floor. Those rocks altered by water are transported to subduction zones by the movement of the tectonic plates. This moves 150-300 metric tons of water per year from the surface to the interior of the Earth, a fairly efficient way to remove water from the surface. That mechanism does not work on Mars because there is no plate tectonics or subduction. The orbiter and robot we have sent to Mars have identified rocks and minerals that formed in the presence of water, including some of the same minerals and rocks that are found on the ocean floor of the Earth. We know that some of these rocks and minerals only form at pressures and temperatures well below the surface of Mars; The water must have been present deep below the surface. As a participating scientist in the InSight mission, I am calculating densities and seismic properties for the possible compositions of rocks on the surface of Mars in order to identify signatures of rocks altered by water that can be detected by seismic waves. Data from the InSight mission could limit the amount of water that can be hidden with the naked eye, within the altered rocks we have observed.
There is and was enough water on Mars. Even today, the Martian polar ice caps are made of enough water ice that, if you melt it all and distribute it evenly around the planet, the global ocean will have a depth of at least 22 meters (72 feet)! However, atmospheric pressure on Mars is so low that liquid water is unstable, so water today is only in the form of ice and a small amount of gas.
In the past, Mars had significantly more liquid water, and it formed rivers, lakes and possibly even oceans on the surface. The Curiosity rover has recently investigated more than 300 meters of rock (more than 1000 feet) that formed at the bottom of a lake that appears to have been stable on the surface of Mars for more than 1 million years, some 3.5 billion years ago. years. This shows that there must have been a thicker atmosphere and more water at the beginning of the history of Mars, but we still do not fully understand how much there was or how long it was stable. So, where was the water? Part of it was lost in space (Mars does not have a magnetic field to protect it from the solar wind), part of the water reacted with volcanic rocks and then became trapped in minerals, and part of the water is still there, frozen in the layers of ice and in the layers of permafrost below the ground.
"Part of it was lost in space … some of the water reacted with volcanic rocks and then became trapped in minerals, and some of the water is still there today, frozen in the layers of ice and in the layers of permafrost below the ground "
Professor of Physics and Deputy Director (Solar System) at Mullard Space Science Laboratory, University College London
Mars has changed significantly in the 4,600 million years since its formation. About 3.8 billion years ago, Mars was much more Earth-like, with volcanism, a magnetic field, water on the surface and a thick atmosphere, at a time when life began on Earth. Evidence of ancient water on the surface has been accumulating, beginning with imaging of the Viking orbiter, direct on-site evidence that the water was on the surface with Opportunity and Curiosity mineral badysis, evidence of neutral acidity, Curiosity water and water Rich mineral and clays in the oldest surface regions, mapped by Mars Express.
Mars is now cold and dry, and has a thin carbon dioxide atmosphere, with a harsh surface environment and a thinning atmosphere unprotected by a global magnetic field. Mars Odyssey and Phoenix found evidence of subsurface water ice, Mars Reconnaissance Orbiter found recurring slope lines that may be signs that water seeps from the sub-surface (or alternatively dust falls) and last year Mars Express found evidence of a & # 39; lake & # 39; of liquid water below the south pole using radar measurements.
All this shows that water has been and still is present on Mars, but some of the water sank and others escaped into space as seen by Mars Express and Maven. But the life potential on Mars was the best of 3.8 billion years ago. That is why with the Rosalind Franklin (ExoMars) rover of the ESA-Russia, we will drill up to 2 m below the hard Martian surface to look for signs of past, or less likely, present life. In addition, Mars 2020 will collect samples for a possible return of Mars sample.
"Mars is now cold and dry, and has a thin atmosphere of carbon dioxide, with a harsh surface environment and an atmosphere that is not protected by a global magnetic field."
Professor, Astronomy, Vanderbilt University, and the author of & # 39; Life on Mars, & # 39; from where the following is drawn
If we take all the water from a planet, place it on the surface of the planet and distribute it evenly in more than 100% of the surface area, we would have what planetary scientists call a "global ocean". This concept helps us easily Visualize the total volume of water on that planet.
Quite solid estimates indicate that the total amount of water that planetary scientists have found on Mars, mainly in the polar ice caps, would create a global ocean with a depth of 70 to 100 feet. That's the amount of water we know Mars has today. We can affirm that with great confidence.
We also know that Mars has lost a lot of water. By using the abundance of certain trace gases important in the atmosphere of Mars today, scientists estimate that Mars once had a global ocean with a depth of approximately 450 feet. Based on this evidence of atmospheric gases, we know that Mars has lost 75% to 85% of the water with which it started. All that water is gone forever, lost in space. Once again, I think we can say this with great confidence.
However, if, in addition to the evidence of atmospheric gases, we use the visual evidence of the water flowing on the surface of Mars, which is clear in the form of dry river valleys and exit channels that mark the ancient surface of the red planet . We can estimate that once Mars had enough water to generate a global ocean with a depth of 1,500 to 3,000 feet. If we use this evidence of the old river valleys and the exit channels, we would necessarily conclude that 40% to 80% of the water with which Mars began does not get lost in space, all that water is hidden from us, within Mars and it's not blocked. in polar ice cream. That is a lot of water.
In total, the evidence (in the current atmosphere) seems to suggest that Mars lost 10% to 30% of the water it had 4 billion years ago. From the remaining 70% to 90% of your water inventory, no more than 5% -10% of that water has been found in the polar ice caps. The remaining water, perhaps up to 90% of the water with which Mars began, is found in underground reservoirs.
Timothy E. Dowling
Professor of Planetary Physics, University of Louisville
Mars is the only other planet in our solar system that has the potential to be habitable for humans, so it is not surprising that every detail that is similar or different to Earth is being studied closely. Although Mars is smaller than Earth, it has the same surface area in terms of dry land (because the surface of the Earth is two thirds of the oceans), which helps explain the size of the task of exploring the geology of Mars.
After more than half a century of interplanetary exploration, we have many independent lines of evidence that once water flowed over the surface of Mars in abundance. From orbit (remote sensing), we have high resolution images that show fluvial characteristics in channels of now dry rivers. From rovers on the ground, we detect aqueous chemistry in several different types of minerals, which are not formed without liquid water, and even soft stones.
We even have brackish water films that flow today on the surface of Mars, where it is warmer near the equator in the middle of the day. This was confirmed by spectroscopy, which found the signal of hydrated salts, very diluted milk of magnesia!, Just where these moist flows appear and not where they do not. But otherwise, where is all surface water on Mars?
A big part of the answer, perhaps most of it, is the fact that Mars is not big enough to have a planetary magnetic field. The molten iron-nickel core of the Earth generates a dynamo that gives the planet of origin a strong magnetic field, which diverts the infinite current of harmful charged particles that flow from the sun, the solar wind. In sharp contrast, Mars has been hit by the solar wind without rest, most likely for billions of years. NASA's MAVEN spacecraft is currently in orbit around Mars and makes detailed measurements of this process, and has confirmed that the solar wind constantly separates the volatiles from Mars.
The image that is emerging is that every detail that can be listed for the Earth is, to a great or lesser extent, beneficial for life, and even missing some of these makes life appear and flourish almost impossible. The beneficial features that the Earth has missing on Mars include a strong magnetic field, a large moon (to provide tides that agitate the chemistry of the ocean, and to stabilize the obliquity or inclination of the planet, and therefore its stations) and the Plate tectonics (to recycle oxygen and other resources back into the ocean's crust). But the more we learn about Mars, the more intriguing the planet becomes.
The last great mystery is that there is a strong and unequal amount of methane in the atmosphere of Mars, much more than expected. On Earth, this is caused in part by geothermal vents, but predominantly by the biosphere. Currently, planetary scientists are devising ways to decipher what is causing the excess methane on Mars, so stay tuned (and participate)!
"Mars is the only other planet in our solar system that has the potential to be habitable for humans."
Professor of Geological Sciences at the University of Colorado and principal investigator of the atmosphere of Mars and the evolution of volatile evolution (MAVEN), whose research focuses on the understanding of the nature of planetary surfaces and atmospheres and the possibility of existence of life in the universe.
The evidence of liquid water in ancient Mars can be seen in the morphology of the surface: characteristics that look like runoff channels for surface water, lakes that filled ancient closed basins created by impact craters, a general degradation of the surface that is more consistent with the presence of an active hydrological cycle, and flow characteristics that suggest the occurrence of large-scale floods.
In addition, rovers have identified minerals on the surface that can only be formed in the presence of liquid water. Some of these are in the form of "concretions," round nodules of minerals that form when water flows through the soil and can dissolve minerals and redeposite them elsewhere.
Today on Mars, we have identified a type of chemical called "perchlorates" mixed with the soil. These minerals can remove water vapor from the atmosphere and dissolve in it to produce small amounts of liquid water that is stable on the surface today at certain times of the Martian day.
More controversial are features such as "ravines" and flow-like features called "recurring slope lines" that may be due to recent water or may be caused by dry flow. And the radar has detected what appears to be a wet layer a kilometer below the surface near the south pole that may involve a layer of underground groundwater.
Today there is water on Mars, in the form of atmospheric water vapor, ice in the polar ice caps, ice buried below the surface in non-polar regions and water contained as part of minerals worldwide. There may also be additional water below the surface, perhaps present as generalized or globally distributed groundwater. Although it is possible, we do not have direct evidence of its existence.
Each of these has been detected by remote sensing observations or directly by images. Much of the water has been divided into its components of hydrogen and oxygen atoms and has been lost in space. We know that this has happened, because it leaves a distinctive signature: deuterium is a heavier form of hydrogen, which has a neutron as well as a proton; As a result of being heavier, it escapes into space less easily and leaves deuterium relatively more abundant in the water that remains on Mars. This enrichment in "D / H" tells us that between 85 and 95% of the water near the surface of Mars has been lost in space.
"Today there is water on Mars, in the form of atmospheric water vapor, ice in the polar ice caps, ice buried below the surface in non-polar regions and water contained as part of minerals worldwide."
Assistant professor of chemistry and biochemistry, Georgia Tech, whose research focuses on the development of tools for in situ organic badysis in the search for extraterrestrial life, among other things.
Water on Earth is still inexplicable. The general problem is that the Solar System seems to be a giant distillation column, with volatile compounds that evaporate to a large extent from the planetary bodies that receive more heat and then accumulate in planetary bodies that are further away and colder. The "ice line" for water seems to be farther away than Earth, so explaining why we have so much could be a bigger challenge than explaining why Mars has so little.
The small size of Mars can not easily be explained without the migration of Jupiter and Saturn inward and then to their current positions, so the original position of Mars can not be known with 100% accuracy until our models and the understanding of the entire solar system improve. Therefore, it is difficult to know how big is the problem of the proportion of water between Earth and Mars, since Mars may have been in any number of places in relation to the Sun before Jupiter and Saturn migrate to their positions current
Another problem is that Mars lost its magnetic field relatively early due to its relatively small size. This causes the solar wind to hit the atmosphere, ionize it and then destroy free protons or molecular hydrogen gas, and even water vapor as a molecular cloud. The MAVEN mission is currently studying this interaction.
"Water really is the ink in the history of Mars."
Assistant Professor, Earth, Atmospheric and Planetary Sciences, Purdue University, whose research program uses data from NASA's satellites and exploration vehicles, along with laboratory and field work on Earth, to understand the processes of the surface that has shaped Mars and the Moon.
Water is really the ink in the history of Mars. We see evidence of all kinds that Mars once had a very active water cycle on the surface, before 3 billion years ago. We see cut river channels in the old highlands, with complicated tributary networks that are only possible if water comes from everywhere at the same time, as expected if rain or snow falls on the surface. These rivers flowed into craters and created deltas in lakes now dry. The Curiosity rover is exploring one of the ancient lake basins in Gale Crater, and has shown that the lake may have been present for hundreds of thousands or millions of years.
We know that the fluid that sculpted the channels and filled the crater lakes was water, and not something more exotic, because we also observe minerals in all the ancient surfaces of Mars that could only have formed in the presence of liquid water. Minerals, such as the salts that form when water evaporates, the clays that form when water stays for a long time, and the carbonates that form when carbon dioxide in the atmosphere dissolves in water. NASA's next rover on Mars, Mars 2020, will look for evidence of ancient life on Mars in the Jezero crater, where a dry lake and the delta may have deposited carbonates and traces of trapped microorganisms.
We know that Mars had abundant water flowing through the surface 3 billion years ago, but now Mars is a cold, hyper-arid planet with very little liquid water on the surface. The reason for this change is that Mars lost almost all of the early atmosphere to space, and the current atmosphere is too thin for liquid water to be stable. NASA's MAVEN satellite has shown that the solar wind and other ongoing slow escape processes are not enough to explain where the atmosphere went, so it is likely that other processes such as giant asteroid impacts will help remove the atmosphere. This has not happened here on Earth because the higher gravity and the active magnetic field help keep the atmosphere around.
Some of the water on ancient Mars was lost in space, but most of the rest froze underground. We see huge reservoirs of ice buried at high latitudes, and NASA's Phoenix landing confirmed that there are deposits of pure ice a few centimeters below the surface. If you melted all the ice buried on Mars, you could easily make an ocean. These ice deposits can be very important for future explorations and human settlements on Mars, as they could provide an easily accessible source of water.
Do you have a hot question for Giz asks? Send us an email to [email protected]