FROZEN SEA AT UTOPIA PLANITIA, MARS
Updated on 1/19/2017
Figure 1 above shows a closeup map of Utopia Planitia where the water ice was found. Figure 2 below shows where Utopia Planitia is with respect to the bulk of the rest of Mars (excluding the poles).
Figure 3 below - See the original caption under the image.
Frozen beneath a region of cracked and pitted plains on Mars lies about as much water as what's in Lake Superior, largest of the Great Lakes, researchers using NASA's Mars Reconnaissance Orbiter have determined.
Scientists examined part of Mars' Utopia Planitia region, in the mid-northern latitudes, with the orbiter's ground-penetrating Shallow Radar (SHARAD) instrument. Analyses of data from more than 600 overhead passes with the onboard radar instrument reveal a deposit more extensive in area than the state of New Mexico. The deposit ranges in thickness from about 260 feet (80 meters) to about 560 feet (170 meters), with a composition that's 50 to 85 percent water ice, mixed with dust or larger rocky particles.
Figure 4 below - See the original caption under the image.
At the latitude of this deposit -- about halfway from the equator to the pole -- water ice cannot persist on the surface of Mars today. It sublimes into water vapor in the planet's thin, dry atmosphere. The Utopia deposit is shielded from the atmosphere by a soil covering estimated to be about 3 to 33 feet (1 to 10 meters) thick.
Our Comment: A soil covering of only 3 feet seems to be very thin when it comes to stopping sublimation. Clarification is needed with respect to how often the soil is this thin vs. how often it's up to 33 feet. The statement about the planet's thin, dry atmosphere leaves out a specific pressure, and our report entitled Mars Correct: Critique of all NASA Mars Weather Data disputes the low pressure that NASA asserts at areoid, however as is seen in Figures 1 and 2 Utopia Planitia is considerably below areoid (in fact, about 7 km below areoid as is shown on Figure 1) meaning that even by NASA standards the pressure will be sufficiently above the triple point (the point at which the temperature and pressure at which the three phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium - for water 273.16 K, 6.11657 mbar) thus enabling both ice and liquid water (when warm enough) to exist at the surface (as it does in conjunction with recurring slope lineae at locations noted on Figure 2). Indeed if we accept the absurdly low NASA-backed pressure of 6.1 mbar at areoid, with a MOLA altitude of 7 km below areoid, as our calculation below reveals the pressure would be up to about 11.66 mbar in Utopia Planitia, but we present evidence in our report to back a real pressure of over 700 mbar.
|ENTERING ARGUMENTS SCALE HEIGHT 10.8 KM AND AVERAGE MARTIAN PRESSURE 6.1 MBAR|
|KILOMETERS||10.8 KM SCALE HEIGHT ||RATIO A/B||=-EXP(C value)||1/D value||PRESSURE MARS BARS ||PRESSURE IN MBAR ||SITE|
|-4.495||10.8||-0.404954955||-0.667006856||-1.499234965||1.499234965||9.145333289||VIKING 2 (latitude 47.97 N (Smith et al. states 47.6680 N), longitude 225.74 W (Smith et al. states 134.0430 E) |
THE NASA ARTICLE CONTINUES: "This deposit probably formed as snowfall accumulating into an ice sheet mixed with dust during a period in Mars history when the planet's axis was more tilted than it is today," said Cassie Stuurman of the Institute for Geophysics at the University of Texas, Austin. She is the lead author of a report in the journal Geophysical Research Letters.Mars today, with an axial tilt of 25 degrees, accumulates large amounts of water ice at the poles. In cycles lasting about 120,000 years, the tilt varies to nearly twice that much, heating the poles and driving ice to middle latitudes. Climate modeling and previous findings of buried, mid-latitude ice indicate that frozen water accumulates away from the poles during high-tilt periods.
Read and Lewis (2004, pp. 269-270)79 note potential reserves of CO2-H2O clathrate in regolith that could raise surface pressure to 200 hPa (mbar) during periods of high-obliquity when, at some point in the future, Mars would have its axis inclined at a greater angle than it has today. If more clathrate is locked up under deeper polar deposits underground, pressure could go as high as 850 hPa (Jakosky et al., 1995).85 But if the soil became rich in water ice through precipitation and adsorption into the porous regolith, Read and Lewis state the value might be limited to 15-30 mbar.
79 Read, P. L., & Lewis, S. R. (2004). The Martian Climate Revisited, Atmosphere and Environment of a Desert Planet, Chichester, UK: Praxis.
85 Jakosky, B. M., Henderson, B. G., and Mellon, M. T. (1995), Chaotic obliquity and the nature of the Martian climate, Journal of Geophysical Research, 100(E1), 1579–1584.
A variation from 15 to 850 hPa (mbar) is obviously huge, but since Read and Lewis indicate that soil rich in water ice through precipitation might limit air pressure to as low as 15 mbar we must point out that such a low pressure does not seem conducive to much precipitation. There has been snow seen falling at the Mars Phoenix lander, but supposedly it not reach the surface. In comparison to the rest of Mars, there are very few craters seen in Utopia Planitia, which seems to suggest a young surface. Since we know that much of the northern hemisphere of Mars was once under water, what we are more likely looking at here is not the result of rain or snow 120,000 years ago. Rather, it is probably an example of the larger sea that once occupied most of the ancient Martian northern hemisphere. It did not all evaporate and fly off into space. Rather, the surface froze and was subsequently covered with a relatively thin layer of dust and dirt. We discussed this in conjunction with our article about Mars MAVEN.
Note that in 2015 NASA Goddard put out an article and video about the ancient Martian ocean. Their article was entitled NASA Research Suggests Mars Once Had More Water Than Earth's Arctic Ocean. The accompanying video is at http://youtu.be/WH8kHncLZwM. Using ratios in waters of deuterium in water to normal hydrogen they determined that Mars had lost 87% of its water to space and that all that remained was frozen at the poles of Mars. However this discovery obviously calls into question their conclusion and begs the question as to how much of what is colored blue in the Northern hemisphere on Figure 2 is, in fact, not just low areas like Utopia Planitia was thought to be, but are in fact also areas where large amounts of ice will be found.
The name Utopia Planitia translates loosely as the "plains of paradise." The newly surveyed ice deposit spans latitudes from 39 to 49 degrees within the plains. It represents less than one percent of all known water ice on Mars, but it more than doubles the volume of thick, buried ice sheets known in the northern plains. Ice deposits close to the surface are being considered as a resource for astronauts.
Figure 5 below - See the original caption under the image.
"This deposit is probably more accessible than most water ice on Mars, because it is at a relatively low latitude and it lies in a flat, smooth area where landing a spacecraft would be easier than at some of the other areas with buried ice," said Jack Holt of the University of Texas, a co-author of the Utopia paper who is a SHARAD co-investigator and has previously used radar to study Martian ice in buried glaciers and the polar caps.
The Utopian water is all frozen now. If there were a melted layer -- which would be significant for the possibility of life on Mars -- it would have been evident in the radar scans. However, some melting can't be ruled out during different climate conditions when the planet's axis was more tilted. "Where water ice has been around for a long time, we just don't know whether there could have been enough liquid water at some point for supporting microbial life," Holt said.
Utopia Planitia is a basin with a diameter of about 2,050 miles (3,300 kilometers), resulting from a major impact early in Mars' history and subsequently filled. NASA sent the Viking 2 Lander to a site near the center of Utopia in 1976. The portion examined by Stuurman and colleagues lies southwest of that long-silent lander.
Use of the Italian-built SHARAD instrument for examining part of Utopia Planitia was prompted by Gordon Osinski at Western University in Ontario, Canada, a co-author of the study. For many years, he and other researchers have been intrigued by ground-surface patterns there such as polygonal cracking and rimless pits called scalloped depressions -- "like someone took an ice-cream scoop to the ground," said Stuurman, who started this project while a student at Western.
Clue from Canada
In the Canadian Arctic, similar landforms are indicative of ground ice, Osinski noted, "but there was an outstanding question as to whether any ice was still present at the Martian Utopia or whether it had been lost over the millions of years since the formation of these polygons and depressions."
The large volume of ice detected with SHARAD advances understanding about Mars' history and identifies a possible resource for future use.
"It's important to expand what we know about the distribution and quantity of Martian water," said Mars Reconnaissance Orbiter Deputy Project Scientist Leslie Tamppari, of NASA's Jet Propulsion Laboratory, Pasadena, California. "We know early Mars had enough liquid water on the surface for rivers and lakes. Where did it go? Much of it left the planet from the top of the atmosphere. Other missions have been examining that process. But there's also a large quantity that is now underground ice, and we want to keep learning more about that."
Joe Levy of the University of Texas, a co-author of the new study, said, "The ice deposits in Utopia Planitia aren’t just an exploration resource, they’re also one of the most accessible climate change records on Mars. We don’t understand fully why ice has built up in some areas of the Martian surface and not in others. Sampling and using this ice with a future mission could help keep astronauts alive, while also helping them unlock the secrets of Martian ice ages.”
SHARAD is one of six science instruments on the Mars Reconnaissance Orbiter, which began its prime science phase 10 years ago this month. The mission's longevity is enabling studies of features and active processes all around Mars, from subsurface to upper atmosphere. The Italian Space Agency provided the SHARAD instrument and Sapienza University of Rome leads its operations. The Planetary Science Institute, based in Tucson, Arizona, leads U.S. involvement in SHARAD. JPL, a division of Caltech in Pasadena, manages the orbiter mission for NASA's Science Mission Directorate in Washington. Lockheed Martin Space Systems of Denver built the spacecraft and supports its operations.
Jet Propulsion Laboratory, Pasadena, Calif.
University of Texas Jackson School of Geosciences