NASA this month released a stunning gravity map of Mars that details the external gravitational forces surrounding the red planet and also provides insight into its interior physical properties. The map is the result of Doppler and range tracking data collected by NASA’s Deep Space Network. Three NASA spacecraft in orbit around Mars participated in the data collection, including the Mars Global Surveyor (MGS), Mars Odyssey (ODY), and the Mars Reconnaissance Orbiter (MRO). More than a decade of data went into generating this high-resolution map.
NASA created this gravity map by plotting the orbital fluctuations of the spacecraft as they circled Mars. Like most planets, Mars has a bumpy surface that affects the gravitational pull experienced by objects in orbit around it. For example, a spacecraft will feel a stronger pull over a mountain and a weaker pull over a canyon. These variations in gravity cause the orbit of the spacecraft to fluctuate. These fluctuations were then monitored by NASA for more than a decade, and the recorded values were used to generate the gravity map. The map required two years of analysis and modeling to confirm which fluctuations were due to gravity and not some other external force or forces.
The map identifies both the high and low points in the gravitational field around the planet. These qualities make it useful to scientists who are sending spacecraft into orbit, allowing them to precisely position the craft so they can collect as much data as possible. It also can be used to explore physical features of the planet, such as the crustal thickness, deep interior, and seasonal variations of dry ice at the poles.
“With this new map, we’ve been able to see gravity anomalies as small as about 100 kilometers (about 62 miles) across, and we’ve determined the crustal thickness of Mars with a resolution of around 120 kilometers (almost 75 miles),” said MIT’s Antonio Genova, who works at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The better resolution of the new map helps [us] interpret how the crust of the planet changed over Mars’ history in many regions.” The research team was able to estimate the amount of carbon dioxide that freezes out of the atmosphere during a Martian winter. They also were able to observe the changes in the north and south poles that occurred with the changing of the Martian seasons.
Genova, along with his colleagues, published the results of their Mars gravitational study on March 5 in an online version of the journal Icarus. Grants to fund the research was provided by NASA’s Mars Reconnaissance Orbiter mission and NASA’s Mars Data Analysis Program.