Astrobiology Workshop, Macquarie University July 12-13 2001

workshop home page | workshop program

BEAGLE 2: The next exobiology mission to Mars

Everett K. Gibson, Jr.(1), Colin T. Pillinger(2), Ian P. Wright(2), Mark R. Sims(3), Andy Morse(2), Jenny Stewart(2), G. Morgan(2), Ian Praine(2) and Dennis Leigh(2)

1 SN2, Planetary Sciences, NASA Johnson Space Center, Houston, TX 77058,

2 Planetary Sciences Unit, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK,

3 Space Research Centre, Univ. of Leicester, Leicester, LE1 7RH, UK.

Beagle 2 is a 60 kg probe (with a 30 kg lander) developed in the United Kingdom for inclusion on the European Space Agency's 2003 Mars Express mission. Beagle 2 will deliver to the surface of Mars a payload of scientific instruments which consists of a very high percentage of science payload to landed spacecraft mass. Beagle 2 will be launched with Mars Express on a Starsem's Soyuz-Fregat rocket in June 2003 from Russia's Baikonur Cosmodrome in Kazakhstan. The launch window is from June 1-11, 2003. Beagle 2 will land on Mars on December 26, 2003 in the Isidis Planitia basin in a landing ellipse centered around 10oN and 275oW. The landing site is a large flat sedimentary basin that overlies the boundary between ancient highlands and the northern plains. Isidis Planitia basin, the third largest basin on Mars, which is possibly filled with sediment deposited at the bottom of long-standing lakes or seas, offers an ideal environment for preserving traces of life. Beagle 2 lander offers a low-cost, decreased risk and increased science return opportunity for the exploration of Mars at a distinct geologically and biologically interesting site. Funding has been finalized for Beagle 2 through the launch phase of the mission and the spacecraft is in its final stages of development and manufacture.

The Beagle 2 probe consists of four components: (1) Entry, descent and landing system (EDLS) derived from concepts proven with Pathfinder, (2) Lander, including scientific instruments, (3) Hold down and release (HRM) and spin up and ejection mechanisms (SUEM), and (4) a orbiter-lander communications relay system. The later two components remain onboard the Mars Express Orbiter.

Beagle 2 was developed to search for organic material and other volatiles on and below the surface of Mars in addition to the study of the inorganic chemistry and mineralogy of the landing site [1]. Beagle 2 will utilize a mechanical mole and grinder to obtain samples from below the surface, under rocks and inside rocks. The lander has a pair of stereo cameras for imaging the surrounding landing site along with a microscope for close examination of surface and rock samples. Analysis will include examination of both rock and soil samples at various wavelengths, X-ray spectrometer and Mossbauer spectrometer as well as a search for organics and other light element species (e.g. carbonates and water) and the measurement of their isotopic compositions. Beagle 2 lander has as its focus the goal of establishing whether evidence for life existed in the past on Mars at the Isidis Planitia site or at least establishing if the conditions were ever suitable. Carbonates were first recognized as existing on mars when they were found in the Martian meteorite Nakhla [2]. Organics associated with carbonates were discovered in 1989 [3]. Romanek et al. [4] showed the carbonates in ALH84001 were formed at low temperatures. McKay et al. [5] suggested there was evidence within the ALH84001 meteorite for possible early life on Mars. Thomas-Keprta et al. [6] showed the presence of unique magnetite biomarkers in ALH84001's carbonates are indistinguishable from those present in magnetotactic bacteria found on Earth. Gibson et al. [7] recently showed there was significant evidence for liquid water and biogenic products present on Mars across a 3.9 billion year period. A time interval for biogenic activity similar to that observed on Earth.

A mechanical arm (PAW) operates from the lander package and is used for science operations along with acquisition of surface samples. Instruments attached to the PAW include the stereo camera system, Mossbauer instrument, X-ray fluoresence instrument, microscope, environmental sensor package, rock corer/grinder, a spoon, mirror, brushes, a mole attachment for acquisition of subsurface to depths of 1 to 2 meters and an illumination device.

Beagle's stereo camera system has a 48o field of view and utilizes 1000 x 1000 CCD arrays. Each camera has 14 filters which have been optimized for mineralogy composition, dust and water vapor detection. The microscope's camera is designed for viewing the size and shape of dust particles, rock surfaces, microfossils, and characteristics of the samples prior to introduction into the gas analysis package (GAP). The camera has a resolution of 4 microns/pixel, features 4 color capability (red, green, blue and UV fluoresence), a depth of focus of 40 micrometers and translation stage of +3 millimeters.

The heart of the Beagle 2's life detection package is the gas analysis package (GAP) which consists of a mass spectrometer with collectors at fixed masses for precise isotopic ratio measurements and voltage scanning for spectral analysis. The primary aim of the GAP package is to search for the presence of bulk constituents, individual species, and isotopic fractionations for both extinct and extent life along with studying the low-temperature geochemistry of the hydrogen, carbon, nitrogen and oxygen components present on Mars from both the surface and atmosphere. The GAP is a magnetic sector mass spectrometer with the range of 1 to 140 amu which can be operated in both the static and dynamic modes. A triple Faraday collector array will be used for C, N and O ratios along with a double Faraday array for H/D. Pulse counting electron multiplier will be utilized for noble gases and selected organics. The anticipated detection limits are at the picomole level for operation in the static mode of operation and high precision isotopic measurements will be made in the dynamic mode. The vacuum system consists of a bellows roughing pump along with two ion pumps. The variable volume bellows has an expansion/ compression factor of approximately 7 for matching gas pressures into the mass spectrometer. Sample processing and preparation system consists of reaction vessels along with references. Sample ovens capable of being heated are attached to the manifold for sample combustion. Surface, subsurface materials and interior rock specimens will be combusted in pure oxygen gas at various temperature intervals to release organic matter and volatiles. Combustion process will permit detection of all forms and all atoms of carbon present within the samples. A chemical processing system is capable of a variety of conversion reactions. Gases are manipulated either by cryogenic or chemical reactions and passed through the gas handling portion of the vacuum system. There are two modes of operation: quantitative analysis and precise isotopic measurements.

Three main types of analysis will be carried out by the GAP: (1) search for organic matter, (2) stepped combustion for total light element content and speciation, and (3) atmospheric analysis. Isotopic measurement of H/D, 13C/12C, 15N/14N, 17O/16O, and 18O/16O and search for possible biogenic methane within the Martian atmosphere will be carried out. Estimates of the present concentration of methane in the martian atmosphere is believed to be <100ppb. The lifetime of methane within the Martian atmosphere is believed to be < 300 years and therefore no abiogenic methane is anticipated in Mars' atmosphere. The Beagle 2 GAP is capable of concentrating atmospheric gases and the search for biogenic methane in Mars atmosphere will be carried out. The mass spectrometer will operate in the static mode for the measurements after chemical reagents have concentrated the methane in the atmosphere. Conversion to a measureable component will be carried out to ensure no false positive results will be obtained along with lowering the detection limits for methane. Should methane be detected within the Martian atmosphere its putative source would have to be biogenic (i.e. methanogenic bacteria).

An environmental sensor system for surface temperatures, atmospheric pressures, wind speed and direction is also to accompany atmospheric sampling. The particle radiation environment will be characterized both in terms of dose and rate. The UV flux at the landing site will be measured in a variety of wavelength bands longer than 200nm, information relevant to understanding the survival of organics. High sensitivity isotopic analysis of the carbon species present within the samples makes no assumptions about the biochemistry on Mars but provides clues to past life as inferred from the isotopic fractionations measured directly on Mars. Isotopic fractionation signatures from biogenic processes will survive even in altered rocks.

Planetary protection protocols will be followed for Beagle 2. The lander has been designated as a Category IVA+ mission. A microbial reduction plan is in place and all components will be sterilized. Contamination and sterilization control procedures are used for the aspectic assembly of the spacecraft along with the microbial assessment of all activities utilizing industrial validation methods. Additional cleaning procedures will be followed to reduce blanks associated with GAP operations.

Beagle 2 is an example of cooperation between its university, industrial, government and scientific partners who are producing a low-cost spacecraft with the highest scientific goals. Follow-on Mars exploration missions utilizing the Beagle concept should be seriously considered for any payload going to Mars in the future.

References:

[1] M.R. Sims et al. (1999), SPIE Conf. on Instruments, Methods and Missions for Astrobiology II, SPIE Vol. 3755, pp. 10-23.

[2] R. Carr et al. (1985) Nature 314, 248-250.

[3] I.P. Wright et al. (1989) Nature 340, 220-222.

[4] C.S. Romanek et al. (1994) Nature 372, 655-657.

[5] D.S. McKay et al. (1996) Science 273, 924-930.

[6] K. Thomas-Keprta (2000) Geochimica et Cosmochimica Acta 64, 4049-4081.

[7] E.K.Gibson, Jr. et al. (2001) Precambrian Research 106, 15-34.