“NEXT (iN situ EXploration of planeTary objects): EUROPA”, a challenge to identify the best Raman technique to explore the surface of Jupiter's moon Europa for future missions.

The María de Maeztu Academy of the Centro de Astrobiología is a two year-long (2019-2020, 2020-2021), tailor-made capacity-building activity implemented within the frame of the “Maria de Maeztu” excellence programme. It aims to strengthen and develop new capacities and stimulate the training of young researchers. The first edition of the transdisciplinary challenges is a training activity of the María de Maeztu Academy intended to develope new skills and generating relevant scientific-technical solutions in the field of Astrobiology. The training program started in September 2021 by forming teams with volunteers from different CAB and INTA departments and different areas of expertise. Throughout 2020-2021, several periodic reviews of the proposals were carried out, passing different milestones and receiving expert comments in each evaluation. Then, the CAB’s MdM Executive Committee decided to financially support the four teams to develop the proposed projects in the 2021/2022 academic year, until the end of the María de Maeztu programme. One of those challenges is “NEXT (iN situ EXploration of planeTary objects): EUROPA” and its objective is to identify the optimal Raman technique for the exploration of the surface of Jupiter´s moon Europa in future missions:

• conducting tests of various Raman techniques (using both commercial and flight models) on representative samples from Europa
• characterizing these samples with the different Raman techniques
• generating a database of pros and cons of each technique, which can minimize risks and optimize expected results

Figure 1 - “NEXT (iN situ EXploration of planeTary objects): EUROPA” logo

In the search for life on other bodies within the Solar System, the top candidates are the icy moons, including Saturn’s moon Enceladus and Europa. These icy moons are target of study as they will help us in the task of assessing possible habitability zones in our neighborhood.

The choice of instruments that can answer these questions and also allow us to understand other factors is key. Raman spectroscopy has the versatility to be used to obtain those answers. It has been widely used in the analysis of terrestrial and planetary samples due to its advantages in rapid and non-destructive analysis of the mineralogy and mineral chemistry of rock and/or soil samples. For planetary explorations it exhibits great potentials for unambiguous phase identification due to its narrow and non-overlapping peak profiles, fast analysis without sample preparations, robust behavior and low mass, etc.

To achieve the stated objectives, a work plan has been established in different stages, subdivided into three phases:

• Samples preparation
• Tests conduction of various Raman techniques on the samples (first  is carried out exclusively at the INTA facilities and in the second, the collaborating laboratories will take part)
• Analysis of the test results and database generation of pros and cons of each technique

The samples prepared consist in a saline solution with a molecular organic component. The salt used was MgSO₄ that was detected by the Galileo mission [1]. The organic molecule selected was the amino-acid alanine. This amino-acid was discovering in several meteorites as the Murchison meteorite [2]. The sample solutions were prepared with proportions in weight of 5, 10 and 17 % for the salt, and 0.5, 1.0 and 1.5 for the alanine.

The following figures show the multisamples compositions of the nine samples (1 to 9), as a result of the prepared sample vials.

Figure 2 - Multisamples concentrations

 

Figure 3 - Prepared multisamples vials

 

In the second phase, the prepared samples will be analysed in liquid and frozen state with different Raman technologies in four laboratories including the ExoMars RLS [3] Flight Spare model located at INTA. RLS [4] was the first Raman spectrometer qualified for space applications. This phase will be completed in June 2022.

The laboratories where the tests will take place together with the Raman technology to be tested are as follows:

• Centro de Astrobiología (CAB): iHR550 Horiba with an in-situ 532nm laser and portable i-Raman BWTEK with an in-situ 532nm laser
• INTA: ExoMars RLS Flight Spare (in-situ visible green laser). GSE (control and scientific analysis) automated by SW
• University of Valladolid: Raman in-situ Exemplar® Plus LS High Performance Spectrometer with an 785nm (IR) laser and Raman with remote pulsed laser
• Instituto de Micro y Nanotecnología (IMN): LabRaman HR with two possibilities: 532 nm Solid State Diode Laser and 632 nm (HeNe) Solid State Diode Laser

 

Figure 4 - portable i-Raman BWTEK at CAB facilities

 

Figure 5 - RLS Flight Spare Model at INTA facilities

 

With all the information provided by the Raman tests with Raman technology, an analysis of the results will be carried out in July 2022 and conclusions will be issued on the different techniques used to determine and argue which technology (remote or in-situ Raman technology, which excitation laser wavelength: visible / infrared spectrum) would be the most suitable for meet the scientific requirements to address whether life exists or has ever existed in Europa.

 

 

[1] Thomas B. McCord, Gary B. Hansen, Jean-Philippe Combe, Paul Hayne, Hydrated minerals on Europa’s surface: An improved look from the Galileo NIMS investigation, Icarus, Volume 209, Issue 2, 2010, Pages 639-650

[2] Engel, M., Nagy, B. Distribution and enantiomeric composition of amino acids in the Murchison meteorite. Nature 296, 837–840 (1982)

 [3] Rull, F., et al, The Raman Laser Spectrometer for the ExoMars Rover Mission to Mars, Astrobiology, 2017, vol. 17(6-7), 627-654

[4] Moral, A.G., et al, A Raman Spectrometer for the ExoMars 2020 Rover, European Planetary Science Congress 2017, 17-22 September, 2017, Riga Latvia, id. EPSC2017-1001