A team of researchers led by Dr. Antonio Genova of NASA’s Goddard Space Flight Center has released a detailed new map of Mars’ gravity.
This view of the Martian gravity map shows the Tharsis volcanoes and surrounding flexure: the white areas in the center are higher-gravity regions produced by the massive Tharsis volcanoes, and the surrounding blue areas are lower-gravity regions that may be cracks in the crust. Image credit: MIT / UMBC-CRESST / GSFC.
The new gravity map was produced using data collected by NASA’s Deep Space Network from three spacecraft in orbit around the Red Planet: Mars Global Surveyor, Mars Odyssey, and the Mars Reconnaissance Orbiter.
“The new map will be helpful for future Mars exploration, because better knowledge of the planet’s gravity anomalies helps mission controllers insert spacecraft more precisely into orbit about Mars,” said Dr. Genova, who is first author of a paper on this research published online this month in the journal Icarus.
The high resolution of the map suggests a new explanation for how some features formed across the boundary that divides the relatively smooth northern lowlands from heavily cratered southern highlands.
“An area of lower gravity between Acidalia Planitia and Tempe Terra was interpreted before as a system of buried channels that delivered water and sediments from Mars’ southern highlands into the northern lowlands billions of years ago when the Martian climate was wetter than it is today,” Dr. Genova and co-authors said.
“The new map reveals that this low gravity anomaly is definitely larger and follows the boundary between the highlands and the lowlands. This system of gravity troughs is unlikely to be only due to buried channels because in places the region is elevated above the surrounding plains.”
“The map shows that some of these features run perpendicular to the local topography slope, against what would have been the natural downhill flow of water.”
“An alternative explanation is that this anomaly may be a consequence of a flexure or bending of the lithosphere due to the formation of the Tharsis region.”
A map of Martian gravity looking down on the North Pole (center): white and red are areas of higher gravity; blue indicates areas of lower gravity. Image credit: MIT / UMBC-CRESST / GSFC.
Also, the scientists confirmed that Mars has a liquid outer core of molten rock by analyzing tides in the Martian crust and mantle caused by the gravitational pull of the Sun and the two small Martian moons.
Finally, by observing how the gravity of the Red Planet changed over 11 years – the period of an entire cycle of solar activity – they inferred the massive amount of carbon dioxide that freezes out of the atmosphere onto a Martian polar ice cap when it experiences winter.
A map of Martian gravity looking down at the South Pole (center): white and red are areas of higher gravity; blue indicates areas of lower gravity. Image credit: MIT / UMBC-CRESST / GSFC.
They also observed how that mass moves between the south pole and the north pole with the change of season in each hemisphere.
“With this new map, we’ve been able to see gravity anomalies as small as about 62 miles (100 km) across, and we’ve determined the crustal thickness of Mars with a resolution of 75 miles (120 km),” Dr. Genova said.
“The better resolution of the new map helps interpret how the crust of the planet changed over Mars’ history in many regions.”
_____
Antonio Genova et al. 2016. Seasonal and static gravity field of Mars from MGS, Mars Odyssey and MRO radio science. Icarus, vol. 272, pp. 228-245; doi: 10.1016/j.icarus.2016.02.050
