MARCH 2018
TOPICAL SIENCE
M A R C H
M. FRANKLIN
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The ExoMars Mission In This Issue Page 1 What is the Exomars Mission? Key Dates in the Mission.
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The ExoMars Rover, due for launch in 2020 The ExoMars Mission is a scientific collaboration between the European Space Agency (ESA) and the Russian agency Roscosmos. There are two phases, the first of which was launched on 14 March 2016, while the second is planned for 2020. The first phase consists of an orbiting laboratory, called the Trace Gas Analyser (TGA), which, as its name implies, will identify trace gases in the Martian atmosphere. At the same time, an Entry, Descent and Landing module (EDL) was designed to land on the Martian surface. Phase 2 will attempt to land a rover on Mars.
KEY DATES 14th March 2016 Phase 1 was launched from the Baikonur cosmodrome in Kazakhstan
Oct. 2016
2020
The TGA and the EDL arrived at Mars & separated. TGA began the aerobraking phase.
The planned launch of the ExoMars rover will take place.
The main Goal of the Mission Role of the TGA
Page 3 Brief History of the planet Mars
Page 4 Conditions on the surface of Mars What the mission has achieved so far.
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MARCH 2018
TOPICAL SCIENCE
M. FRANKLIN
The Scientific Goals of the ExoMars Mission The principal goal of the ExoMars mission is to search for evidence that life may have existed on the planet Mars at some time in the past. Chemical analysis of the atmosphere, surface dust and rocks will be conducted, adding to our previous store of knowledge of Mars. The TGA (Trace Gas Analyser) will ‘sniff out’ the atmosphere for traces of gases, such as methane, that may have been produced by living organisms. Previous missions have shown that at present, there is frozen water on Mars, both underground and in the polar ice caps, which are mainly composed of ‘dry ice’ or solid carbon dioxide. But there is also evidence that liquid water once flowed over the surface. The presence of water in the liquid state is a pre-requisite for life, as we know it. Now that we know that life could have existed on Mars, to satisfy their curiosity, scientists want to know if it actually did. Finding signatures of life would demonstrate that Mars is capable of supporting living organisms, which would strengthen the possibility of establishing a human colony on Mars at some time in the future. Many people, scientists and non-scientists alike, believe that this is worth exploring.
Reull Vallis. Credit: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO
The Great Equatorial Rift Valley The NASA Viking 1 Orbiter took this picture in 1976. It shows the famous ‘rift valley’ on the Martian equator, known as ‘Valles Marineris’. https://www.popsci.com/best-imagesmars-so-far#page-7 2
MARCH 2018
TOPICAL SCIENCE
M. FRANKLIN
The picture on the left shows three volcanoes that erupted during the so-called ‘Noachian Period (4.1 – 3.7 Billion years ago). Part of Olympus Mons, the highest mountain in the solar system, is seen at the top left of the image, but this did not form until later, during the more recent Amazonian Period, which has lasted from 2.9 Billion Years ago to the present. The Noachian Period was followed by the Hesperian Period (3.7 to 2.9 Billion Years ago.)
The Natural History of the Planet Mars Geologists have been able to describe the physical processes that occurred, over billions of years, which gave rise to the various rocks and surface features on our planet Earth. Planetary scientists have attempted to do the same for Mars. However, they have the disadvantage that they do not actually live on Mars and so they cannot do field work in the same way that Earth geologists can. They depend on pictures sent back by the various missions as well as samples analysed by robots. There are also over 120 meteorites than have landed on Earth and which, it is believed, have come from Mars. From this evidence, the history of Mars over the past 4.5 billion years has been deduced. It is reasonable to assume that the four rocky planets in our solar system, Mercury, Venus, Earth and Mars, were formed at around the same time, so we can get an estimate of the age of Mars from this assumption. But with limited amount of samples, it has not yet been possible to verify the age of Mars by radiometric dating, as is routine for geological samples collected on Earth. One way to get an idea of the age of the planet is to count the number of visible craters; since, the older a planet, the longer it would have been exposed to bombardment from asteroids and meteorites and therefore the older it is. While we can assume that the planet formed about 4.5 billion years ago, along with the other rocky planets, it is evident that its surface has been eroded over time and renewed in places. The southern hemisphere has an older surface crust than the northern hemisphere, as it has a greater density of craters. It also has the highest mountains, mainly of volcanic origin. It is estimated to have an age of 3.8 billion years. The northern hemisphere has younger rocks, with vast plains created by volcanic lava flows. During the early periods, Mars was subjected to heavy bombardment from asteroids and meteoroids. There was also much volcanic activity, creating mountains, while surface cracks produced great rifts. Mars no longer has any active volcanoes.
This picture of the ‘Valles Marineris’ was taken by Mariner 9, on January 12, 1972. It appeared in ‘Science Horizons’, February 1971, Published by the U.S. Information Service. For more information on this historic Mars Mission visit the NASA website: https://www.jpl.nasa.gov/missions/mariner-9mariner-i/ 3 3
MARCH 2018
TOPICAL SCIENCE
M. FRANKLIN
Present Conditions on Mars Mars is much smaller than our home planet Earth. Its equatorial radius is only 3392 km, compared to 6378 km for Earth. Its surface area is 1.49 x 1014 m2, which is roughly the same surface area as our continents. Its mean density is 3930 kg/m3 and most importantly, for Mars missions, its acceleration due to gravity is only 3.7m/s, much less than on Earth. On the other hand, the atmospheric pressure on Mars is only 0.006 that of Earth! This means that while the low gravity could make for a gentler landing when falling from a height, the thin atmosphere does not provide much air resistance for a parachute landing. The mean surface temperature of Mars is very cold compared to that of Earth. It is only about 210 K, so it is not surprising that we don’t find any liquid water on the surface. Any water on the surface of Mars is now frozen solid. The polar icecaps contain a mixture of water ice and solid carbon dioxide. The principal gas making up the thin atmosphere is also carbon dioxide. Mars does not have a detectable magnetic field, but the Mars Global Surveyor found strip-like magnetization of alternating polarity on the surface of Mars. This is evidence that Mars at one time had a magnetic field, which changed orientation from time to time. The lack of a magnetic field leaves the surface of Mars unprotected from cosmic rays, the solar wind and particles thrown out during coronal mass ejections. This could cause the malfunction of instruments being used to investigate Mars.
EDLSchiaparelli Crash landing. The mission did not all go according to plan. Unfortunately, the Schiaparelli lander crashed on Mars, because of a computer software problem. It is hoped this can be corrected, so that the Rover, due to launch in 2020, does not suffer the same fate. The lander was named after the Italian who first reported seeing ‘canali’ (channels) on Mars. English speakers wrongly concluded they had been constructed by intelligent beings !
What the mission has achieved. Phase 1 reached Mars, as planned, in October 2016. The Entry, Descent & Landing Module (EDL), nicknamed Schiaparelli, separated and the Trace Gas orbiter began the aerobraking phase. This used the atmospheric drag to gradually lower the TGA into orbits closer and closer to the surface of the red planet. This phase has been successfully completed. Watch this space for further updates!
Author : Margaret Franklin, retired chemistry lecturer and science communicator.
For more information on the ExoMars Mission, visit the ESA website: http://exploration.esa.int/mars/46048-programme-overview/ 4