With less than a year away for the next Mars rover mission of Mars 2020, it seems that a quick overview of one of the science payloads is worth mentioning. Mars 2020 is expected to launch next July with a landing on Mars in Feb of 2021. Some of the most exciting scientific experiments relate directly to exoastronomy. For the mission, the search for biosignatures is Science Goal #1.Attempting to detect both past and present biosignatures is no easy feat considering how difficult it is to measure and not contaminate the samples. For the 2020 science team, "a biosignature (a 'definitive biosignature' or DBS) is an object, substance and/or pattern whose origin specifically requires a biological agent. Examples of DBS are complex organic molecules and/or structures whose formation and abundances relative to other compounds are virtually unachievable in the absence of life." (Mustard et al. 2013). But, how to achieve a DBS is the problem.
We've seen some false positives/tentative results decades before through the Viking Mars missions--such as the metabolic reaction in the Labeled-Release experiment (still controversial) and failure of the gas chromatograph mass spectrometer (GCMS) to detect organics. But, both the Mars Global Surveyor and Mars Exploration Rovers demonstrated Mars was wet in the past hinting at the strong possibility of life during a warmer, wetter period.
For Mars 2020, the primary biosignature instrument will be SHERLOC or the Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals. Raman spectroscopy utilizes a laser to interact with the vibrational and rotational states of molecules which shift the scattered photon frequency. For SHERLOC this is a 248.6 nm UV laser which provides both fluorescence and resonant Raman scattering at a wavelength suited to condensed carbon and aromatic organics. The good news is that the power level of the UV laser can be low enough to reduce concern on heating and/or destroying the organic samples.
It's important to note that a detection of a DBS does not complete the 'life on Mars' journey. There is still a second stage to secure a sample, seal it in containers and make it available for return to Earth in future missions thus allowing for more definitive analysis. Small steps but important ones.
No comments