These colorful maps of Mars are the most accurate depiction of how gravity varies around the Red Planet. Created by measuring subtle variations in the gravitational field experienced by NASA spacecraft as they zip past the planet, the images allow us to understand what lurks inside better than ever.
The map was created using data gathered from Mars Global Surveyor (MGS), Mars Odyssey (ODY), and the Mars Reconnaissance Orbiter (MRO). Subtle differences in the gravitational field cause minute changes in the trajectory of the spacecraft. Those differences can be measured, geotagged, compiled, and over time used to create these maps.
Using three satellites provides a means of verification, but the process was a slow one: The maps are made up of almost 16 years worth of data. And because the variations in measurement are so small, the NASA-MIT team that processed the data had to carefully scrutinize and process it—which took two years itself.
The scientists are already using the maps to get a better understanding of the planet. For instance, the data can be used to understand gravitational anomalies over the surface of the planet—some as small as 62 miles across—as well as allowing the team to calculate the thickness of the planet’s crust with more accuracy than before. In fact they can measure the crust thickness with a resolution of 75 miles, helping them understand what causes the variation in gravity as well as confirming previous results that found Mars to have a liquid outer core of molten rock.
The variations in gravitational field over time have also allowed the team to predict that 3 to 4 trillion tons of carbon dioxide freezes out of the atmosphere onto the northern and southern polar caps during a Martian winter. That’s about 12 to 16 percent of the mass of the entire atmosphere.