A group of planetary scientists using data from the Thermal Emission Imaging System (THEMIS) onboard NASA’s Mars Odyssey orbiter has created the most detailed global map yet made of Red Planet’s surface properties.
Unlike an ordinary daytime photo, this nighttime image of Martian surface shows how warm various surface areas are: brighter tones mean warmer temperatures, which indicate areas with rockier surface materials; darker areas indicate cooler and dustier terrain. Image credit: NASA / JPL-Caltech / Arizona State University.
The new map uses nighttime temperature images to derive the thermal inertia – a calculated value that represents how fast a surface heats up and cools off – for areas of Mars, each the size of a football field.
“We used more than 20,000 THEMIS nighttime temperature images to generate the highest resolution surface property map of Mars ever created,” explained team member Dr Robin Fergason at the U.S. Geological Survey’s Astrogeology Science Center in Flagstaff, Arizona.
As day and night alternate on Mars, loose, fine-grain materials such as sand and dust change temperature quickly and thus have low values of thermal inertia.
Bedrock represents the other end of the thermal inertia range: because it cools off slowly at night and warms up slowly by day, it has a high thermal inertia.
“Darker areas in the map are cooler at night, have a lower thermal inertia and likely contain fine particles, such as dust, silt or fine sand. The brighter regions are warmer, she explains, and have surfaces with higher thermal inertia. These consist perhaps of coarser sand, surface crusts, rock fragments, bedrock or combinations of these materials,” Dr Fergason said.
A version of the map optimized for scientists is available at the U.S. Geological Survey.
“The map has an important practical side. NASA used THEMIS images to find safe landing sites for the Mars Exploration Rovers in 2004, and for Curiosity, the Mars Science Laboratory rover, in 2012,” Dr Fergason said.
“THEMIS images are now helping NASA select a landing site for its next Mars rover in 2020.”
