Just a few decades ago, we knew that Mars was the dusty red sister planet to Earth, but we had no real idea as to what the surface looked like. Now, we have a rover trudging its way over the red rocks (taking selfies along the way), providing us with billion-pixel panoramas. We even have maps of the Martian surface that look about as detailed as any map you’ll ever see of Earth. Last week, NASA released our most accurate map of the Martian surface to date, and it was all done using thermal imaging.
The Curiosity rover isn’t the only extraterrestrial machine we have exploring the surface of Mars. NASA’s Mars Odyssey orbiter is constantly swinging around the red planet, taking images and reporting back to us. To make a detailed map of the planet’s surface, Odyssey used the Thermal Emission Imaging System (THEMIS)–a nine-band visual and infrared camera–to look at how the different surface materials heated and cooled as day transitioned to night. The hi-res image below uses 20,000 THEMIS pictures:
THEMIS took thousands of pictures of Mars, each covering about a football field’s worth of area, to determine the total “thermal inertia” of the surface. Thermal inertia is a measure of how fast different materials heat up and cool down. The more thermal inertia a surface has, the longer it takes for that surface to change temperature as day changes into night on Mars. From thermodynamics we know that materials like bedrock hold heat better. They have a higher thermal inertia. Finer materials like sand and dust don’t hold heat as well and therefore have a lower thermal inertia. By calculating these differences, scientists at the USGS Astrogeology Science Center in Flagstaff, Arizona and researchers at ASU’s Mars Space Flight Facility were able to produce the map above.
“A tremendous amount of effort has gone into this great global product, which will serve engineers, scientists, and the public for many years to come,” said principal investigator Philip Christensen in a NASA press release.
Maps like this one aren’t just pretty. Scientists have already used maps like these, and will use this new map going forward, to determine the geologic history of the Martian surface and to inform landing sites for Mars missions. We used thermal inertia maps to pick landing sites for the Mars Exploration Rovers in 2004, and for Curiosity in 2012. When the next Mars rover mission launches in 2020, our scientists are sure to gawk at this gorgeous map again.