Selecting the landing site for 2018 ExoMars Rover

This post was contributed by Birkbeck student, Anja Lanin. Anja attended Dr Peter Grindrod’s lecture, ‘Selecting the landing site for 2018 ExoMars Rover’ during Birkbeck Science Week 2016.

Mars and a rover

Over the last two years, specialist teams in Europe have been working on helping ESA select the landing site for the first European rover on Mars. This is not just a project for PhD-holders, even individual research findings from undergraduate students contribute to the realisation of this mission. Birkbeck students and staff, including the presenter of this talk, Dr Peter Grindrod, have been closely involved. In his talk ‘Selecting the landing site for the ESA 2018 ExoMars rover’, Dr. Grindrod not only brought to light the difficulties in finding an appropriate site in unexplored regions of Mars but also emphasised the problem of balancing safety, and scientific output.

Birkbeck on Mars!

Birkbeck scientists have been directly involved in developing the PanCam stereo-camera system, which is part of the ExoMars instrument payload, led by UCL’s Mullard Space Science Laboratory. This camera will be crucial for understanding the context of rocks and samples investigated by ExoMars.

Risky goals

The ‘search for signs of past and present life on Mars’ is the main goal of this mission, according to Dr Grindrod. The one billion Euro investment will initially rest on the Russian Proton rocket, with an 89% success rate, on the scheduled May 2018 launch date. The precious 300kg solar-powered rover payload is to land on Mars about 7 months later, via parachute and retro-rockets.

Dr Peter Grindrod

Dr Peter Grindrod

Looking for life, but where?

We learn from Dr Grindrod that the rover needs to land on some of the oldest Martian rocks (>3.6 billion years). Why? Geochemical analysis using orbital-based technology indicates that rocks in some of these oldest regions are sedimentary and characterised by hydrated (clay) minerals.

We know that on Earth clay minerals form from the interaction of rocks with water that is neutral in pH and suits terrestrial life. Some of the geologically younger rocks on Mars contain sulfate minerals formed under water-poor conditions and around life-unsuitable acidic water. So we need a site, as Dr Grindrod says, that at one point had some life-friendly water flowing through it depositing soft sedimentary rocks that the rover can get to and drill into.

Access forbidden – the contamination problem

According to Dr Grindrod, the rover is prohibited from landing in what are called ‘Mars Special Regions,’ areas where any terrestrial organisms unintentionally carried by the rover may survive. Thus areas potentially containing terrestrial life-supporting liquid water at present are a no-go. So scientists have been looking for a rover touch-down location in areas where there may have been life in the past but probably not at present.

Zooming in on a landing target

Mars isn’t small, but temperature constraints rule out areas near the cold poles and the seasonally warm southern hemisphere. Equally very hilly areas are also rover unsuitable due to the steep slopes. Keeping these constraints in mind, the most promising geological outcrops scientists were left with covered just 2% of Mars’ surface area. Finally, they had to consider that the rover could land anywhere within a still considerably large ca. 104 x 19 km elliptical area, rather than a particular spot.

Watch Dr Grindrod’s lecture

The chosen few

Two of the eight landing site proposals submitted throughout Europe came from the UK and both made it into the final four.

In the end a site called Oxia Planum was chosen as the destination for the 2018 launch. The location appears to be near the end of an ancient delta-like river drainage network and there may even be different layers present containing different types of clay minerals, possibly suggesting groundwater interaction. However, one problem with this landing site is that some of the surface is covered in small wind ripples – could the small 20 cm ExoMars rover wheels get stuck here??

For the back-up launch date in 2020 two back-up sites have been selected, Mawrth Vallis and Aram Dorsum. The latter location would place the rover near deposits of one of the oldest river systems (now inverted) on Mars and any landing spot would be conveniently located no more than 100 m from a relevant deposit.

Mars, the red planetWhat’s next?

If Oxia Planum for some reason is proved to be not to be safe enough more work is needed to decide which of the back-up sites is best for the alternative 2020 launch. In the end this decision will be up to ESA and the Russian Space Agency.

Let’s remember though, as pointed out by Dr Grindrod, once the rover touches down the scientific results are for us, for every scientist involved, for everyone whose money has contributed to the mission, not just the investors but also the public.


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