New Mars Gravity Map Provides Glimpse Into Hidden Interior

Data from Three NASA Spacecraft Provides Most Detailed Mars Gravity Map Ever 

​Spacecraft don't always go where you expect them to...

Even if everything works perfectly, gravity fluctuations from large masses on a planet or moon can pull vehicles off course.

Mars is no different.

With massive features like Olympus Mons, the largest mountain in the solar system, NASA spacecraft have experienced slight course variations as they have orbited Mars over the years.

Mars gravity map looking down at the north pole

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. Credits: MIT/UMBC-CRESST/GSFC Click for larger image.

Now, scientists at Goddard Space Flight Center have used these slight orbital fluctuations to create the most detailed Mars gravity map ever compiled.

The Mars gravity map provides fresh insights into much of the planet's hidden interior, including the thickness of the outer crust and the impact of seasonal variations of dry ice at the poles.

The new gravity map should also help put future spacecraft into orbit more precisely -- a pretty important piece of navigation when you are operating equipment 80 million miles away from home.

As Antonio Genova (MIT), lead author of a paper on the research that was published March 5 in the journal Icarus, said:

The new gravity 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.
Mars gravity map - south pole

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. Credits: MIT/UMBC-CRESST/GSFC Click for larger image

The Mars gravity map was created by using Doppler and range tracking data collected by three NASA spacecraft in orbit around Mars: Mars Global Surveyor (MGS), Mars Odyssey (ODY), and the Mars Reconnaissance Orbiter (MRO). 

Slight differences in Mars' gravity changed the trajectory of these spacecraft, which altered the signal they sent back to Earth. Over a period of 16 years, these small fluctuations were used to build a map of the Martian gravity field -- and provide the most detailed resolution ever of the Red Planet.

This improved resolution also suggests how some features formed across the planet -- particularly at the boundary that divides the relatively smooth northern lowlands from heavily cratered southern highlands.

In addition, by analyzing the tides in the outer layers of the planet (the crust and the mantle) caused by the sun and Mars' two moons, the research team was able to confirm that Mars has a liquid outer core of molten rock.

​As Genova addded:

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).  The better resolution of the new map helps interpret how the crust of the planet changed over Mars' history in many regions.

Want a little more information? Take a look at this short video from NASA to see more detail about their research.

Header image credit: MIT/UMBC-CRESST/GSFC

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