The European Space Agency's ExoMars Trace Gas Orbiter (TGO) is to conduct its final aerobraking manoeuvre this evening prior to starting its mission of sniffing for Martian methane.
TGO should finally settle into its proper orbit tonight, 400km above the red planet. It was launched nearly two years ago aboard a Russian Proton rocket, along with the Schiaparelli lander (which created its own crater on the surface of Mars in October 2016).
The aerobraking technique uses tiny amounts of atmospheric drag on the orbiter’s 17.5m solar panels to adjust the orbit and carry out some bonus science on the dynamics of the Martian atmosphere. It is the first time ESA has attempted to use aerobraking as the primary method to get into a science orbit around a planetary body, although the technique is not entirely novel, having been used by NASA for missions such as Mars Global Surveyor and Magellan.
Starting in March 2018, boffins will use data received from spectrometers and infrared instruments (NOMAD and ACS) onboard the 3,732kg orbiter to search for traces of methane and capture snaps from a camera, capable of taking images at a resolution of 5 metres per pixel, to give context to the readings.
Sadly, the imagery will be insufficient to determine if any methane emissions are coming from a nervous NASA Rover worried about its fate or angry Martians ejected from the Mars leg of a Dubai-bound Transavia flight.
It should, however, be enough to provide imagery of more common trace gas sources, such as volcanoes.
The hunt for methane is an important one, since the gas is destroyed on Mars by ultraviolet light from the Sun in as short a time as 400 years. Whatever remains should be mixed uniformly throughout the atmosphere.
However, ESA’s Mars Express and ground observations have hinted at variations in concentration of methane in the atmosphere that vary with location and time.
Boffins theorise that there may be two potential sources of this methane. The geological explanation calls for a reaction between water and the mineral olivine occurring as part of active underground volcanic processes. Alternatively, biology may be at work with either frozen methane produced by long dead organisms being released over time or actively flatulent microbes roaming the subsurface of the planet.
The mission is expected to last until 2022, with the orbiter acting as a data relay for ESA's 2020 Mars Rover mission. ®