Instrument enables Martian rovers to date rock samples in situ
Mars is a promising location to unravel the mystery of whether life has existed elsewhere in the universe. Evidence suggests that as the red planet was once full of water, with a thicker atmosphere and warmer climate, it may have once been habitable. For planetary scientists, volcanoes, meteor impact craters, signs of atmospheric or photochemical effects and geophysical processes, all carry traces of Martian geological and climate history. So rock samples collected on the Martian surface could yield details about the formation and evolution of Mars, also explaining why it has less atmosphere than Earth, while Martian water might offer clues as to how life could have evolved. “Understanding Martian geophysical, geological and atmospheric processes will also likely reveal details about Earth’s evolution and history, along with that of other Solar System planets,” says Roberto Filippone, project coordinator of the IN TIME project, which was funded by the Marie Skłodowska-Curie Actions programme. Yet, currently, once collected, Martian rock samples have to be sent back to Earth for detailed analysis, increasing time and cost. This inspired IN TIME to design an instrument that uses luminescence to date samples in situ; a solution demonstrated with a portable prototype, dubbed ‘IN TIME’. “Once integrated into a rover, alongside gathering new Martian data, our instrument can help identify the most promising samples to be further analysed on Earth,” explains Filippone from ALMA Sistemi, the project host.
The miniaturised luminescence dating instrument
Luminescence dating exploits the fact that buried Martian samples that have not been exposed to solar radiation, are affected by radioactive isotopes which decay over time and are absorbed by the samples, creating a trapped charge. These charges emit a luminescent signal when stimulated by light, with its intensity indicating the sample’s age. The project used a protocol known as the ‘single-aliquot regenerative-dose (SAR) protocol’, which plots luminescence on a so-called dose-response curve, to simulate the passage of time and give a more accurate age estimate. The project’s prototype instrument comprised three key components necessary to undertake the SAR protocol: the irradiation unit (administering a known dose), light stimulation system (for optical and infrared stimulated luminescence) and photomultiplier (which acquires the luminescence signal), all controlled by project-developed software. The prototype was tested on Earth where it was used to analyse, for the first time, basalt-derived deposits (sedimentary rocks similar to those on Mars) at the ALMA laboratory, supervised by University of Sassari researchers, to validate the results. “We successfully completed all stages of the SAR protocol, demonstrating that it is possible to date basalt-derived deposits using luminescence,” notes Filippone.
Applications coming over the horizon
The instrument was also successfully trialled on Lanzarote to define the chronology of sedimentary deposits and related climatic events, during glacial-interglacial stages over the last 130 000 years in the El Jable plain. Additionally, Martian sites where promising samples are likely to be found, have been characterised by the team, along with a demonstration that the IN TIME instrument can work at low power, on very old and raw (not chemically treated) samples, reinforcing its suitability for Martian work. This could significantly contribute to the European Space Agency’s work in preparation for its vision of sending Europeans to Mars by 2040. “We are now working to produce an autonomous high-performance competitive tool. As well as for Mars, this could be used on Earth. It could date geological deposits/sediments up to 1 million years old and complement archaeological radiocarbon dating, which is limited to 50 000 years and requires organic content,” concludes Filippone.
Keywords
IN TIME, Mars, rover, basalt, samples, luminescence, sedimentary rocks
