ILMA Ion Laser Mass Analyser In-Situ Characterization of a Near Earth Object (NEO) for the MARCO POLO mission

International audienceLike other small bodies of the Solar System, asteroids are the remnants of planet formation. Their compositions are inherited from the Solar Nebula at the time of planetesimal accretion into planets, 4.5 billion years ago. They are valuable objects to assess the physicochemical conditions prevailing at the time and place of their formation in the Solar Nebula. Among them, some are known to be rich in carbon and volatile species (including water), which suggests that they never underwent major heating and differentiation events. Their organic content is also of prime interest because the chemical evolution leading to life on Earth may have been initiated by the delivery of extraterrestrial organic compounds into primitive oceans. For these reasons, ESA and JAXA are studying the feasibility of a joint European-Japanese sample return mission to a primitive carbonaceous Near-Earth Object (NEO): MARCO POLO. Its goal is to characterize a NEO at multiple scales via in-situ measurements by a science payload onboard an orbiter and a lander, and to bring samples back to Earth (Barucci et al. 2009). ILMA is a concept for a new generation high resolution mass Orig Life Evol Biosph 571 spectrometer, proposed to be part of the lander payload of the MARCO POLO mission. This instrument will be a Fourier Transform ion trap mass spectrometer using either Secondary Ion Mass Spectrometry (SIMS) or Laser Desorption Mass Spectrometry (LDMS) into a single platform. To this end, an Orbitrap mass analyser (developed by the Thermofisher Company) will be coupled to a primary ion source and/or a laser source, respectively. The sample will be exposed to the ion and/or laser beam producing sputtered ionized ions which will be collected into the ion trap using the orbital trapping method. Ions will be stabilized in the trap by purely electrostatic quadro-logarithmic electrical fields and the detection undertaken by a non destructive measurement of the ion oscillation frequency inside the trap. Indeed, the trapped ions induce a periodic signal converted using Fourier Transform (FT) into an ultra-high mass resolution spectrum (M/M>60,000 up to m/z=400 amu) (Makarov 2000; Hu et al. (2005). Moreover, ILMA is planned to become one of the lightest (2.7 kg), smallest (15×15×5 cm^3 without the electronic box) and low power consumption (around 12 Watts) mass spectrometer ever achieved for space. Therefore ILMA will constitute a significant progress compared to previous mass spectrometers in space. ILMA will be able to measure in situ chemical (mineral and organic) and isotopic compositions of the NEO, and should bring a new light of their astrobiological relevance for the study of the origin of life on Earth