ESA’s ExoMars Orbiter Sends First Images from Its New Orbit around Mars
ESA’s ExoMars Trace Gas Orbiter (TGO) has sent back its first, color images of Mars from its new, near-circular orbit.
A few weeks ago, TGO reached its final orbit after a year of ‘aerobraking.’ This exciting operation saw the spacecraft skimming through the very top of Mars’ upper atmosphere, using drag on its solar wings to transform its initial highly elliptical 4-day orbit of about 124-61,000 miles (200-98,000 km) into the final, much lower and near-circular path at about 249 miles (400 km).
“This is a major milestone for our ExoMars program. We have reached this orbit for the first time through aerobraking and with the heaviest orbiter ever sent to the Red Planet, ready to start searching for signs of life from orbit,” said TGO mission manager Dr. Pia Mitschdoerfer.
“We will start our science mission in just a couple of weeks and are extremely excited about what the first measurements will reveal,” said TGO project scientist Dr. Håkan Svedhem.
“We have the sensitivity to detect rare gases in minute proportions, with the potential to discover if Mars is still active today — biologically or geologically speaking.”
TGO’s primary goal is to take a detailed inventory of trace gases — those that make up less than 1% of the total volume of the planet’s atmosphere. In particular, the orbiter will seek evidence of methane and other gases that could be signatures of active biological or geological activity.
TGO is set to analyze the Martian atmosphere, in particular trace gases like methane. Although making up a very small amount of the overall atmospheric inventory, methane in particular holds key clues to the planet’s current state of activity. This graphic depicts some of the possible ways methane might be added or removed from the atmosphere. One exciting possibility is that methane is generated by microbes. If buried underground, this gas could be stored in lattice-structured ice formations known as clathrates, and released to the atmosphere at a much later time. Methane can also be generated by reactions between water and olivine-rich rocks, perhaps in combination with warmer, volcanic environments. Again, this could be stored underground in icy cages, and outgassed through cracks in the surface — or through volcanoes. UV radiation can both break down the methane and generate it through reactions with other molecules or organic material already on the surface, such as comet dust falling onto Mars. Methane can also be quickly distributed around the planet by strong winds, ‘diluting’ its signal and making it challenging to identify individual sources. Methane on Mars is expected to have a rather short lifetime — around 400 years — so any detections imply it must have been produced or released relatively recently. TGO will build up a picture over time of the methane distribution, to understand geographic and seasonal distributions, and eventually home in on areas where it might be originating. The spacecraft has the capability to detect and analyze methane and other trace gases, even in low concentrations, with an improved accuracy of three orders of magnitude compared to previous measurements. Furthermore, it will be able to detect key ‘isotopologues’ of methane and water (isotopologues are molecules that have at least one atom with a different number of neutrons than the parent chemical species) to help distinguish between the different formation scenarios. Image credit: ESA / ATG Medialab.
One of TGO’s four instruments, the Colour and Stereo Surface Imaging System (CaSSIS), was activated on March 20.
On April 15, CaSSIS took a stunning image — which features part of an impact crater — during the instrument’s test period.
“We transmitted new software to the instrument at the start of the test phase and after a couple of minor issues, the instrument is in good health and ready to work,” said CaSSIS principal investigator Dr. Nicolas Thomas, from the University of Bern in Switzerland.
TGO’s CaSSIS camera captured this view of the rim of Korolev crater on April 15, 2018. The image is a composite of three images in different colors that were taken almost simultaneously. Image credit: ESA / Roscosmos / CaSSIS.
“The image captures a 25-mile (40 km) long segment of ice-filled Korolev crater located high in the northern hemisphere,” TGO scientists said.
“The bright material is ice that can be seen on the rim of the crater, which is much larger than the image.”
“The picture has a resolution of just over 16 feet (5 m) and outperforms the resolution of images from Hubble and other telescopes by far. In the future, CaSSIS should operate from slightly lower altitudes to give resolutions of less than 16 feet.”
“We were really pleased to see how good this picture was given the lighting conditions,” said Dr. Antoine Pommerol, a member of the CaSSIS science team.
“It shows that CaSSIS can make a major contribution to studies of the carbon dioxide and water cycles on Mars.”