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Posts Tagged ‘ExoMars’

The Schiaparelli space probe has been in the news quite a lot this last week or so. It was due to land on the surface of Mars last Wednesday (19 October), but lost contact about one minute before this. On Friday (21 October) NASA released images taken by its Mars Reconnaissance Orbiter which have led ESA to conclude that Schiaparelli exploded on impact, probably due to a failure of the thruster rockets which were meant to guide it gently down over its last few kilometres of descent. For more on that story, see here. This separate story suggests that the failure of the thruster rockets to burn correctly was due to a computer glitch, and that they only burned for 3 seconds instead of the intended 29 seconds.

What has received far less attention than Schiaparelli is the larger spacecraft which transported it to Mars – the Trace Gas Orbiter (TGO). The TGO was successfully put into orbit about Mars after it and Schiaparelli separated. Whilst ESA scientists worried about the silence of Schiaparelli, they were nevertheless jubilant that the TGO had successfully manoeuvred into orbit about the red planet.

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ESA’s Trace Gas Explorer (TGO) transported the lander Schiaparelli to Mars, and is now successfully in orbit about the red planet.

The TGO’s primary scientific mission is to look for traces of methane emanating from Mars. This is of great scientific interest, because methane could be due to life on Mars. Many bacteria on Earth, in particular those that respire anaerobically, emit methane. The best known example are the bacteria which help digest food in the stomachs of many animals, including us. This is why cows are one of the primary sources of methane emission, the gas is coming from the bacteria in their stomachs.

Methane was first detected in the Martian atmosphere in 2003 by NASA scientists. The following year NASA’s Mars Express Orbiter and some ground-based observations detected methane at the level of about 10 parts per billion. Large temporal and positional variations in the methane concentration were measured between 2003 and 2006, which suggests that the methane is  both seasonal and local.

The other possible source of methane is geological activity. Any methane in the Martian atmosphere is quickly broken down by ultraviolet light from the Sun (there is no ozone layer to protect the molecules from UV light, as there is on Earth). This means that any methane present in the Martian atmosphere but have been recently produced. So, how can we tell the difference between methane due to bacteria and methane due to geological activity?

The key is to look for the presence of other gases along with the methane. If the methane is geological in origin it will be accompanied by sulphur dioxide. If, however, it is due to bacteria it will be accompanied by ethane and other similar molecules. The TGO will be able to measure both the methane and these other gases, and so hopefully will help us determine the origin of the methane. In addition, it will be able to measure and image other things, including sub-surface hydrogen down to a depth of a metre. This will help us better map out the amount and extent of subsurface water ice on Mars.

In all, the TGO has four scientific instruments on it, namely

  1. The Nadir and Occultation for Mars Discovery (NOMAD). This instrument has two infrared and one ultraviolet spectrometer channels.
  2. The Atmospheric Chemistry Suite (ACS) has three infrared spectrometer channels.
  3. The Colour and Stereo Surface Imaging System (CaSSIS) is a high-resolution colour stereo camera which will be able to resolve down to a resolution of 4.5 metres on the Martian surface. Being stereo, it will be able to create an accurate elevation map of the Martian surface.
  4. The Fine-Resolution Epithermal Neutron Detector (FREND), a neutron detector which can indicate the presence of hydrogen in the form of water or hydrated minerals. FREND can detect hydrogen down to a depth of 1 metre in the Martian surface.

NOMAD and ACS are the two instruments which will measure the methane and other trace molecules in the atmosphere. Twice each orbit, when the Sun is both rising and setting as seen from the TGO, it will use the passage of the Sun’s light through the Martian atmosphere to detect and measure the presence of trace molecules, down to a few parts per  billion (ppb).

The TGO will orbit Mars at an altitude of 400 km, in a circular orbit taking only 2 hours to orbit once. The orbit will be inclined at 74 degrees to the Martian equator.  It was launched on the 14 March, so took just over 6 months to get to Mars. In 2021 ESA plans to land a rover on the Martian surface, but whether this schedule is delayed due to the failure to successfully land Schiaparelli remains to be seen.

 

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As of 7:30am BST (06:30 GMT) this morning (Thursday 20 October), it is not looking hopeful for the European Space Agency’s Schiaparelli probe. ESA will make a press announcement at 08:00 GMT, when hopefully we will have a better idea of what has happened. As Schiaparelli was descending it should have been sending telemetry data to its mother ship, the Trace Gas Orbiter (TGO). Those telemetry data were relayed back to Earth overnight, so they should be able to give us a much clearer picture of Schiaparelli’s descent to the surface. 

A large ground-based radio telescope in India was able to detect some of the signals that Schiaparelli was sending to the TGO, and certain key events such as the parachutes opening seem to have occurred. But, communication seems to have ceased some 30-60 seconds before Schiaparelli was expected to reach the surface. That, and its subsequent silence, are not good signs and the fear is that the probe has crashed during its final descent. 

I will update this blogpost when we know more, later this morning. In the meantime, keep your fingers crossed. 

***UPDATE***

I’ve just finished watching the live ESA press announcement. The bottom line is that we still don’t know what has happened to the probe. From the telemetry analysed, ESA say that the parachute opened, and all seemed fine until the parachute detached. Loss of signal happened about 50 seconds before the expected touchdown. Nothing has been heard from Schiaparelli since. ESA also suggested that they knew that the rockets to slow its final descent had fired, but at this point in time they do not know how many of the rockets fired or for how long. 

In addition to various satellites which are in orbit around Mars, in addition to the TGO, trying to communicate with Schiaparelli, NASA’s Mars Reconnaissance Orbiter will take images of the landing site to try to find the probe. The same satellite successfully spotted Beagle 2 a few years ago after it went missing in 2003. 

ESA very much put a positive spin on events, emphasising the success of the TGO, and that the telemetry data from Schiaparelli’s decent should help them fully understand what went wrong. They therefore feel that its possible failure should not alter the schedule to send the ExoMars Rover in a few years. 

I will blog more about the science that the TGO plans to do next week, and give an update (if there are any development) on Schiaparelli. 

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Tomorrow (Wednesday 19 October) the European Space Agency (ESA) will attempt to land its probe Schiaparelli on the surface of Mars. Schiaparelli is named after the 19th Century Italian astronomer  Giovanni Schiaparelli who is most famous for observing “canali” on the surface of Mars in 1877. Whereas the word means “channels” in English, it got mis-translated as “canals”, and led to a furore of interest in the possible existence of artificial irrigation channels which it was suggested had been built by Martians to transfer water from the poles to the arid equatorial regions.

All of this was, of course, wrong; but it led to a surge of interest in Mars, including Percival Lowell establishing his observatory in Flagstaff and spending decades observing the red planet. It was this observatory which in the 1910s found the first evidence for the redshift of spiral nebulae (Vesto Slipher), and where, in 1930, Pluto was discovered.

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Tomorrow (Wednesday 19 October) the European Space Agency will attempt to land its probe Schiaparelli on the surface of Mars.

ESA has only attempted once before to land a spacecraft on the surface of Mars; Beagle 2 crash landed in December 2003 and failed to operate. Schiaparelli is a 600-kg lander which is being transported to Mars by its mother ship, the Trace Gas Orbiter. Both are part of ESA’s ExoMars project, which will put a rover on the surface of Mars in 2021.

Schiaparelli is what is referred to as a “demonstrator”, as its purpose is to test various technologies for the landing of the ExoMars rover in 2021. It is planned that Schiaparelli will only operate for a few days, but I suspect that it will end up operating for longer than this. Let us hope that it has a better landing that Beagle 2!

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