The James Webb Space Telescope will soon be the largest infrared space observatory in the world. The latter will look in particular at the objects furthest from our Universe, but not only. During its first year of service, the instrument will also focus on Mars, with (hopefully) some pretty awesome discoveries.
Mars is today only a cold, dry and desert world, with a carbon dioxide atmosphere 100 times thinner than Earth’s, but this was not always the case. Previously, the red planet was wet, it even contained water and had a thick atmosphere. NASA’s James Webb Space Telescope, scheduled for launch in spring 2019, will study this transition in its first year of operation. The red planet will be targeted by the “future most powerful telescope in the world” from May to September 2020.
“Webb will make extremely interesting measurements of the chemistry in the Martian atmosphere,” says Heidi Hammel, planetologist and executive vice president of the Association of Astronomical Research Universities (AURA) in Washington DC. “And more importantly, these data will be immediately available to the global community to enable them to plan even more detailed observations in future cycles.” Jim Green, director of NASA’s Planetary Science Division, says he is impatient: “I know these observations will be fantastic, with immediate potential for scientific discovery.”
Six active spacecraft are currently in orbit around Mars, plus two surface rovers. If the red planet is to this day the most studied body of our system, the James Webb Telescope and its numerous instruments will allow scientists to study the planet under a completely new eye. One of the major assets will be the ability of the telescope to take snapshots of the entire disk of Mars, something impossible today with orbiters – let alone with rovers. Nor will it be subject to the interferences of our atmosphere, which today affect measurements on the ground from Earth. Webb will also benefit from excellent spectral resolution, which relates to the ability to measure small differences in wavelengths of light.
Observing Mars with this tool will not be easy. “Webb is designed to be able to detect extremely weak and distant targets. Mars, on the other hand, is brilliant and very close,” says Geronimo Villanueva from the NASA Goddard Space Flight Center. As a result, the observations will be carefully calculated to avoid overwhelming the instruments with sunlight.
Much of Mars water has been lost over time due to the Sun’s ultraviolet light, which breaks water molecules. Researchers will be able to estimate this amount of disappeared water by measuring the abundance of H2O and heavy water (HDO) in the Martian atmosphere. The preferential escape of hydrogen (lighter over time) would then lead to an asymmetric ratio of H2O and HDO on Mars, indicating the amount of water that escaped into space. The telescope will be able to measure this ratio at different times, different seasons and different locations.
Although most of the water on Mars is enclosed in ice, it is possible that liquid water may still exist in underground aquifers. These potential reservoirs could even accommodate life. In 2003, astronomers detected methane in the Martian atmosphere. Methane is potentially generated by bacteria here, but could also come from geological processes. Webb’s data will surely provide new clues as to its origin.