ExoMars

ExoMars (Exobiology on Mars) is a European-led robotic mission to Mars currently under development by the European Space Agency (ESA) and NASA. Originally conceived as a rover with a static ground station, ExoMars was planned to launch in 2011 aboard a Soyuz Fregat rocket.^[7] Within the framework of the new Mars Joint Exploration Initiative signed by NASA and ESA in July 2009, the drastically delayed ExoMars mission was combined with other projects to a multi-spacecraft programme divided over two Atlas V-launches:^[4] the Mars Trace Gas Orbiter (TGM) was merged into the project, piggybacking a static meteorological lander being slated for launch in 2016. In 2018 the original robotic ESA-rover will be launched, possibly together with a smaller NASA rover called Mars Astrobiology Explorer-Cacher (MAX-C).^[6]

Background and mission history

Since its beginnings in the early 2000s, ExoMars was subject to massive political and financial strife. Originally, the ExoMars concept consisted of one single, large robotic rover being part of ESA's Aurora programme as a Flagship mission and was approved by Europe's space ministers in December 2005. Initially planned to launch in 2011, Italy, a leading nation on the ExoMars mission, decided to limit its financial contribution, causing the first of three delays.

In 2007 Canadian-based technology firm MacDonald, Dettwiler and Associates Ltd. (MDA) announced that is has won a one-million-euro contract with EADS Astrium of Britain to design and build a prototype Mars rover chassis for the European Space Agency, which will be used in the upcoming ExoMars mission.^[8]

In July 2009 NASA and ESA agreed upon a new Mars Joint Exploration Initiative, significantly altering the technical and financial setting of the ExoMars mission. On June 19, when the rover was still planned to piggyback on the Mars Trace Gas Orbiter, it was reported, that a prospective agreement would require that ExoMars lose enough weight to fit aboard the Atlas vehicle with NASA's orbiter.^[9]

In August 2009 it was announced that the Russian Space Agency Roscosmos and ESA had signed a collaboration agreement that includes cooperation on two Mars exploration projects: Russia's Phobos-Grunt project and ESA's ExoMars. Specifically, ESA secured a Russian Proton rocket as a backup launcher for the ExoMars rover, which should also include Russian-made parts.^[10][11]

In October 2009 it was reported that under the agreed Mars Joint Exploration Initiative, the mission will be split into two parts: a lander/orbiter mission in 2016 and a rover mission in 2018, each with a significant NASA role, including the use of two Atlas V rockets.^[1][12] This initiative would apparently reconcile technological and science goals with available budgets.^[12]

On December 17, 2009, the ESA governments gave their final approval to a two-part Mars exploration programme to be conducted with NASA, confirming their commitment to spend €850 million ($1.23 billion) on missions in 2016 and 2018. Another €150 million needed for operating the mission will be solicited during a meeting of ESA government ministers in late 2011 or early 2012. Unlike some ESA programmes, the ExoMars financing will not include a 20 % margin for cost overruns, however.^[13]

Mission objectives

The ExoMars mission's scientific objectives, in order of priority, are:^[14]

• to search for possible biosignatures of Martian life, past or present.
• to characterise the water and geochemical distribution as a function of depth in the shallow subsurface.
• to study the surface environment and identify hazards to future manned missions to Mars.
• to investigate the planet's subsurface and deep interior to better understand the evolution and habitability of Mars.
• achieve incremental steps ultimately culminating in a sample return flight.

The technological objectives to develop are:

• landing of large payloads on Mars.
• to exploit solar electric power on the surface of Mars.
• to access the subsurface with a drill able to collect samples down to a depth of two metres (just below the degradating reach of UV light, oxidants and ionizing radiation.)^[15]
• to develop surface exploration capability using a rover.

Mission architecture

According to current plans,^{[4][6][16][17]} the ExoMars mission will comprise three, possibly four, spacecraft elements sent in two launches, both from Florida:

Contributing agency	First launch in 2016	Second launch in 2018
	Launch vehicle: Atlas V 411	Launch vehicle: Atlas V 551
	One unspecified TGM-payload	Landing system: Sky-crane
		65 kg Mars Astrobiology Explorer-Cacher (Max-C)-rover
	Trace Gas Mission (TGM) orbiter	270 kg ExoMars rover
	600 kg static meteorological lander
	Entry, descent and landing system (EDL)

2016 launch

Mars Trace Gas Mission orbiter

The Mars Trace Gas Orbiter.

The Mars Trace Gas Mission (TGM) orbiter, to be launched on January 2016,^[15] will deliver the ExoMars static lander (a meteorological station) and then proceed to map the sources of methane on Mars and other gases, and in doing so, help select the landing site for the ExoMars rover to be launched on 2018. The presence of methane in Mars' atmosphere is intriguing because its likely origin is either present-day life or geological activity. Upon the arrival of the rover(s) in 2018/2019, the orbiter would be transferred into a suitable lower orbit where it would be able to perform analytical science activities as well as operate as a data-relay satellite. Its operation may be extended to serve future missions well into the 2020s.^[16]

Static lander

Originally, this static lander was planned to carry a group of eleven instruments collectively called the "Humboldt payload"^[18] that would be dedicated to investigate the geophysics of the deep interior, but a payload confirmation review in the first quarter of 2009 resulted in a severe descope of the lander instruments, and the Humboldt geophysical suite of lander instruments was cancelled entirely.^[19] Although the recent partnership with NASA and the decision to launch all mission elements with two rockets has generated new payload reviews, it was decided to first demonstrate ESA's new descent and landing system technology on the lander, so its payload will be very limited.^[2]

The Entry, Descent and Landing Demonstrator Module (EDM) will provide Europe with the technology for landing on the surface of Mars with a controlled landing orientation and touchdown velocity. After entering the Martian atmosphere, the module will deploy a parachute and will complete its landing by using a closed-loop Guidance, Navigation and Control system based on a Radar Doppler Altimeter sensor and on-board Inertial Measurement Units. The latter will guide a liquid propulsion system which will produce a semi-soft touchdown on the surface of Mars by the actuation of clusters of thrusters to be operated in pulsed on-off mode.^[20]

The EDM lander is expected to survive on the surface of Mars for a short time (about 8 sols) by using the excess energy capacity of its batteries.^[20] Its proposed landing site is the Meridiani Planum because it is almost flat and without too many rocks, ideal for its airbag landing system.^[2]

2018 launch

Current plans call for the use of NASA's sky crane entry, descent and landing (EDL) system to deliver both rovers together on the surface of Mars.^[15]

If there will be two rovers delivered to the same location on Mars, Their science objectives and instruments will be complementary in order to minimise duplication. Advantages of operating two rovers in the same area are: rover to rover imaging, cross analysis of similar geological targets, may include a low-frequency ground-penetrating radar on MAX-C and listen with WISDOM on ExoMars to construct rover to rover subsurface transects, and the MAX-C could receive and cache some of the most valuable subsurface samples collected by ExoMars.^[15]

ExoMars rover

An outdated ExoMars rover model at the ILA 2006 in Berlin

The ExoMars rover is a highly autonomous six-wheeled terrain vehicle and will weigh 270 kg, ca. 100 kg more than NASA's Mars Exploration Rovers Spirit and Opportunity.^[5] Temporary plans considered a downsized version with a reduced weight of 207 kg.^[21] Instrumentation will consist of the 10 kg 'Pasteur Payload' containing, among other instruments, a 2 meter sub-surface drill.^[22]

The carrier module will deliver the descent module to Mars from a hyperbolic approach trajectory after which the Sky-crane landing system will ensure a soft landing with high accuracy. Once safely landed on the Martian surface the solar powered rover would begin a 180-sol (6 months) mission. To counter the difficulty of remote control due to communication lag, ExoMars will have autonomous software for visual terrain navigation using compressed stereo images from mast mounted panoramic and infrared cameras and independent maintenance. For this purpose it creates digital maps from navigation stereo pair cameras and autonomously finds the adequate trajectory. Close-up collision avoidance cameras are used to ensure safety enabling the vehicle to navigate and safely travel approximately 100 meters per day. After the lander has been released and landed on the surface of Mars, the Mars Trace Gas Orbiter will operate as the rover's data-relay satellite.^[16]

MAX-C rover

Schematic depiction of the proposed Mars Astrobiology Explorer-Cacher (MAX-C)-Rover

The current proposal is that ExoMars may be joined by a slightly smaller NASA rover; this additional rover may be the Mars Astrobiology Explorer-Cacher (MAX-C).^[6][23][24] The fact that for the first time two rovers will be active at the same location is expected to lead to synergies, such as bistatic radar surveys between the two rovers. The MAX-C rover would collect, analyse, and cache the most valuable samples in a manner suitable for return to Earth by a future mission.

Launch vehicle

Under the agreed collaboration, NASA will provide two Atlas V rockets, as it was decided to divide the weight of the ExoMars system in two launches.^[17][25][26]

ESA has already worked out a framework agreement with the Russian Space Agency that would allow it to cooperate on ExoMars, including provision of backup launch services and a payload contribution, along with mission support.^[26] The backup launcher is the Proton rocket,^[11] which is a four-stage rocket that was previously used to launch the Salyut 6, Salyut 7, Mir and some International Space Station components.

Landing system and proposed landing sites

If the collaboration with NASA takes place as proposed, it would be possible to implement NASA's new skycrane entry and descent system, as used on the Mars Science Laboratory rover.^[27]

Mawrth Vallis with its potential clues on the history of water on Mars is a landing site-candidate.

As of November 2007, the potential landing sites are:^[28]

• Mawrth Vallis
• Nili Fossae
• Meridiani Planum
• Holden Crater
• Gale Crater

However, the 2009 discovery of methane sources on the planet makes them a high value target for exploration.^[1] The presence of methane is intriguing because its likely origin is either present-day life or geological activity; confirmation of either would be a major discovery. Methane occurres in extended plumes, and the profiles imply that the methane was released from discrete regions. The profiles suggest that there may be two local source regions, the first centered near 30° N, 260° W and the second near 0°, 310° W.^[29] To determine the optimal landing site and secure telecommunications, it was decided to include the Mars Trace Gas Mission orbiter in the 2016 launch in order to map beforehand what appears to be seasonal methane production.^[30] The rover could then investigate the methane sources identified by the orbiter.

Instrumentation of the ExoMars rover

The present environment on Mars is exceedingly hostile for the widespread proliferation of surface life: it is too cold and dry and receives large doses of solar UV radiation as well as cosmic radiation. Notwithstanding these hazards, basic microorganisms may still flourish in protected places underground or within rock cracks and inclusions.^[30] The science package in the ExoMars rover will hold a variety of instruments to study the environment for past or present habitability and possible biosignatures on Mars. The first instrument proposal (2004) is as follows:^[31]

Imaging system

The Panoramic Camera System (PanCam) has been designed to perform digital terrain mapping for the rover and to search for morphological signatures of past biological activity preserved on the texture of surface rocks. The PanCam assembly includes two wide angle cameras for multi-spectral stereoscopic panoramic imaging, and a high resolution camera for high-resolution colour imaging.^[32][33] The PanCam will also support the scientific measurements of other instruments by taking high-resolution images of locations that are difficult to access, such as craters or rock walls, and by supporting the selection of the best sites to carry out exobiology studies.

Drill

The ExoMars core drill is devised to acquire soil samples down to a maximum depth of 2 metres, in a variety of soil types. The drill will acquire a core sample (1 cm in diameter x 3 cm in length), extract it and deliver it to the inlet port of the Rover Payload Module, where the sample will be distributed, processed and analyzed. The ExoMars Drill embeds the Mars Multispectral Imager for Subsurface Studies (Ma-Miss) which is a miniaturised IR spectrometer devoted to the borehole exploration. The system will complete experiment cycles and at least 2 vertical surveys down to 2 metres (with four sample acquisitions each). This means that a minimum number of 17 samples shall be acquired and delivered by the drill for subsequent analysis.^[34]

Analytical laboratory instruments

These instruments are placed internally and used to study collected samples:^[35]

• Mars Organic Molecule Analyzer (MOMA) consists of a laser desorption ion source and a GC-MS spectrometry. The laser desorption ion source is capable to evaporate organic molecules even if they are not volatile, while the GC separates the highly volatile small molecules within the gas chromatograph. The final analysis of both instruments is done with an ion trap mass spectrometer.

• Infrared imaging spectrometer (MicrOmega-IR) is an infrared imaging spectrometer that can analyse the powder material derived from crushing samples collected by the drill. Its objective is to study mineral grain assemblages in detail to try to unravel their geological origin, structure, and composition. These data will be vital for interpreting past and present geological processes and environments on Mars. Because MicrOmega-IR is an imaging instrument, it can also be used to identify grains that are particularly interesting, and assigned them as targets for Raman and MOMA-LDMS observations.

• Mars X-Ray Diffractometer (Mars-XRD) - Powder diffraction of X-Rays will give exact composition of the crystalline minerals.^[36][37] This instrument includes also an X-ray fluorescence capability that can provide useful atomic composition information.^[38]

• Raman spectrometer (Raman) will provide geological and mineralogical context information complementary to that obtained by MicrOmega-IR. It is a very useful technique employed to identify mineral phases produced by water-related processes.^[39][40][41]

• Ground-penetrating radar, called WISDOM (for Water Ice and Subsurface Deposit Information On Mars) will explore the subsurface of Mars to identify layering and help select interesting buried formations from which to collect samples for analysis.^[42] It can transmit and receive signals using two, small Vivaldi-antennas mounted on the aft section of the rover. Electromagnetic waves penetrating into the ground are reflected at places where there is a sudden transition in the electrical parameters of the soil. By studying these reflections it is possible to construct a stratigraphic map of the subsurface and identify underground targets down to 2 to 3 m depth, comparable to the 2-m reach of the rover's drill. These data, combined with those produced by the PanCam and by the analyses carried out on previously collected samples, will be used to support drilling activities.^[43]

• Mars Multispectral Imager for Subsurface Studies (Ma-MISS) is an infrared spectrometer located inside the drill. Ma-MISS will observe the lateral wall of the borehole created by the drill to study the subsurface startigraphy, to understand the distribution and state of water-related minerals, and to characterize the geophysical environment. The analyses of unexposed material by Ma-MISS, together with data obtained with the spectrometers located inside the rover, will be crucial for the unambiguous interpretation of the original conditions of Martian rock formation.^[44]

Autonomous navigation

The ExoMars Rover is designed to navigate autonomously across the surface. A pair of stereo cameras allow the Rover to build up a 3D map of the terrain, which the Navigation software then uses to assess terrain around it so that it avoids obstacles and find the most efficient route. ^[45]

See also

• Astrobiology
• Mars Astrobiology Explorer-Cacher (MAX-C rover)
• Life on Mars
• Mars Trace Gas Mission

References

External links

• Scientific Management Plan
• ESA Main site
• Aurora Flagship mission page (including ExoMars)
• ExoMars-Pasteur Progress Letters
• Pasteur Payload Package-Instrument Definition Document (PDF) Note: the document is of considerable size
• Pasteur Newsletter 5
• Raman-LIBS spectrometer for ExoMars Combined Raman-LIBS spectrometer for ExoMars at TNO
• EADS Astrium ExoMars Rover Vehicle

Spacecraft missions to Mars Flybys Mariner 4 · 6 · 7 · Mars 4 · Rosetta · Dawn Orbiters Mariner 9 · Mars 2 · 3 · 5 · Viking 1 · 2 · Phobos 2 · Mars Global Surveyor · 2001 Mars Odyssey · Mars Express · Mars Reconnaissance Orbiter Landers Mars 3 · Viking 1 · 2 · Mars Pathfinder · Phoenix Rovers Sojourner · Mars Exploration Rovers (Spirit · Opportunity) Future missions Mars Science Laboratory (2011) · Fobos-Grunt / Yinghuo 1 (2011) · MetNet (2011-2019) · Northern Light (2012) · MAVEN (2013) · Mars Trace Gas Mission (2016) · ExoMars static lander (2016) and rover (2018) · Mars Astrobiology Explorer-Cacher‎ (2018) · Mars sample return mission (2018+) · Manned mission (2030+) Related topics Exploration · Colonization · Failed Mars missions · Mars Scout Program Bold italics indicate active missions