The inside of Mars is full of secrets. Via NASA/JPL
It’s been almost 40 years since humans started exploring Mars up close, with landers and rovers on the surface and probes in orbit. And we’ve gained a fair, though still incomplete, picture of what’s happening on Mars. But what’s happening inside Mars remains a mystery.Studying the insides of a far-away planet is far from a simple proposition. But the European Space Agency’s Mars Express orbiter has started shedding some light on Mars’ inner workings by cleverly looking inside the planet using radio waves.
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We don’t know a lot about the interior of Mars, though we do know the planet's core has a radius somewhere between 930 and 1,300 miles, or about half the planet's total radius of about 2,106 miles. Scientists found this core by observing and measuring the way Mars rotates around its axis. A planet’s movements are influenced by the material inside it, and Mars‘s rotation suggests that there’s something dense at its core with less dense layers stacked between it and the Martian surface.But that’s about all we know, which means delving further into Mars’ mysterious innards is bound to be among the central science goals of future missions to the red planet. Understanding the internal structure of Mars will help us understand how its atmosphere formed and how the planet evolved into a cold, likely dead, and nearly atmosphere-free world. And of course, learning about Mars’s evolution will tell us a lot about Earth’s.
An artist's concept of the Mars Express Orbiting circling the red planet. via
NASA’s InSight mission, an acronym for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport, is going to start probing into the mystery of the Martian interior. (Literally!) The lander is going to jam long probes into the surface to gather seismic data. But that’s a ways off; InSight is set to launch in March of 2016.In the mean time, ESA’s Mars Express is peeking under Mars’s surface. The orbiter, which arrived at Mars in 2003, can’t see all the way down to the Martian core but it can look miles below the surface. The key is sending low frequency radio waves towards the planet using the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument, which turned on and became operational in 2005.
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For the most part, these radio waves are reflected off the planet's surface. But some get through, traveling deeper and bouncing off subsurface layers of rock, water, or ice. Mars Express measures the strength and timing of the radar echoes that arrive back at the orbiter to determine just what type of material the radio waves are bouncing off of. From there, it can create an underground map of sorts, like the one below.
The ESA's subsurface map of Mars's southern highlands. via
This is a radar image of a nearly 3,500 miles long slice through Mars’s southern highlands. On the right is the vast Hellas Basin, a nearly 1,500 mile wide basin that goes almost 4.5 miles deep into the Martian surface, making it one of the largest impact basins in the Solar System.The bright peak left of center is Mars’s south polar region where, beneath the cap of frozen carbon dioxide and water ice, the radar revealed are multiple layers of ice and dust thought to have accumulated as Mars went through a cyclical climate change in its history. Scientists have also been able to estimate the amount of water trapped in frozen layers at Mars’ south pole: roughly equivalent to a 36 foot deep liquid layer covering the entire planet. That’s a pretty significant amount of subsurface water.It’s sort of incredible that Mars Express has managed to map the layers under the surface of Mars, but really, we’ve only scratched the subsurface.
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