A world workforce led by scientists from the College of Liège has noticed, for the primary time within the seen vary, a glow on the night time facet of the planet Mars. These new observations present a greater understanding of the dynamics of the higher ambiance of the Crimson Planet and its variations all year long.
A scientific workforce led by researchers from the Laboratory for Planetary and Atmospheric Physics (LPAP) on the College of Liège (BE) has simply noticed, for the primary time, lights within the night time sky over Mars utilizing the UVIS-NOMAD instrument on board the Hint Gasoline Orbiter (TGO) satellite tv for pc of the European House Company (ESA). This instrument is a part of the NOMAD spectrometer suite developed on the Royal Institute for House Aeronomy in Uccle, and examined and calibrated on the Liège House Centre. It was inserted into round Martian orbit at an altitude of 400 km in 2008.
Initially designed to map the ozone layer surrounding the planet within the ultraviolet, UVIS-NOMAD covers a spectral vary extending from the close to ultraviolet to pink. For this goal, the instrument is often oriented in the direction of the centre of the planet and observes daylight mirrored by the planetary floor and ambiance. Based mostly on a proposal from our laboratory, the instrument was oriented in the direction of the limb of the planet as a way to observe its ambiance from the sting,” explains Jean-Claude Gérard, planetologist at ULiège. Again in 2020, we have been already in a position to detect the presence of a inexperienced emission between 40 and 150 km in altitude, current in the course of the Martian day. This was as a result of dissociation of the CO2 molecule, the primary constituent of the ambiance, by ultraviolet photo voltaic radiation.”
A protracted journey for oxygen atoms
The TGO satellite tv for pc, when observing the ambiance at night time, has simply detected a brand new emission between 40 and 70 km altitude. This emission is as a result of recombination of oxygen atoms created in the summertime ambiance and carried by the winds in the direction of the excessive winter latitudes,” explains Lauriane Soret, a researcher at LPAP. There, the atoms recombine on contact with CO2 to reform an O2 molecule in an excited state that relaxes and emits gentle within the seen vary.” This gentle emission is concentrated within the polar areas to the north and south, the place the oxygen atoms converge within the downward department of the large trajectory from the other hemisphere. The depth of the emission is excessive, within the seen vary. This course of appears to be reversed each half Martian 12 months*, and the luminosity then adjustments hemisphere. An analogous emission was analysed on Venus by the identical workforce utilizing pictures from the Venus Specific satellite tv for pc. On Venus, the atoms journey from the sunlit facet to the darkish facet the place they emit the identical glow as on Mars.
ULiège researchers on the forefront
LPAP researchers performed a key function in these observations. After highlighting the presence of a layer of inexperienced gentle surrounding the planet on the day facet, they recognized the night-time emission. The research might be continued in the course of the TGO mission and can present us with priceless details about the dynamics of the Martian higher ambiance and its variations over the course of the Martian 12 months,” continues Lauriane Soret. We’ve observed that one other ultraviolet emission as a result of nitric oxide (NO) molecule can also be noticed by UVIS in the identical areas. Evaluating the 2 emissions will allow us to refine the analysis and establish the processes concerned.
The NO molecule additionally emits gentle when oxygen and nitrogen atoms recombine. As with the radiation from the O2 molecule, the atoms are fashioned in daylight, transported by the winds to the opposite hemisphere and recombine in the course of the downward movement within the polar areas.
These new observations are surprising and fascinating for future journeys to the Crimson Planet,” enthuses Jean-Claude Gérard. The depth of the night time glow within the polar areas is such that straightforward and comparatively cheap devices in Martian orbit may map and monitor atmospheric flows. A future ESA mission may carry a digicam for world imaging. As well as, the emission is sufficiently intense to be observable in the course of the polar night time by future astronauts in orbit or from the Martian floor’.
Benoit Hubert, researcher at LPAP, concludes: “Distant sensing of those emissions is a wonderful software for probing the composition and dynamics of Mars’ higher ambiance between 40 and 80 km. This area is inaccessible to direct strategies of measuring composition utilizing satellites”.
(* A Martian 12 months lasts 687 Earth days.)