Testing the applicability of NEWTON Susceptometer for fast and in-situ determination of the magnetic susceptibility, in meteorite samples and a Martian terrestrial analogue.

• Introduction

The characterization of the complex magnetic susceptibility (real and imaginary parts) of rocks is an unexplored tool to constrain the composition, structure and geological history of rocks in surface planetary exploration. We propose the NEWTON susceptometer for the determination of the complex magnetic susceptibility, to provide valuable information about the regolith and surface rocks in rocky bodies of the solar system, to be used as a selection criterion of rocks for sample return missions or for the in-situ scientific studies of the magnetic properties during planetary missions [1]. The instrument is based on AC - inductive methods, and its dynamic range of the real susceptibility covers magnetic susceptibility values for rocks from the Earth, Moon and Mars [2, 3, 4]. The sensor is suitable to be placed on board rovers, or to be used as a portable device during field campaigns and by astronauts in manned space missions. This sensor provides a great advantage compared to available commercial susceptometers due to its robustness, compatibility with the planetary environments and that it does not require sample preparation, but only minimum sample dimensions (~50 x 20 x 20 mm). 

The aim of this work is to test the capability of the instrument in two different scenarios with distinct types of samples representative of a wide susceptibility range: 1) the in-situ real magnetic susceptibility determination in Cerro Gordo volcano, considered as a terrestrial analogue [5]; and 2) the characterization of meteorites from the collection of the Museo Geominero (Madrid, Spain).

The first study case consists of an intraplate volcano, with potential similar composition and structure of volcanoes from Mars. The second study case comprises various meteorite samples of different origins. 

2.1 Terrestrial analogue: Cerro Gordo volcano

Cerro Gordo volcano was proposed as a Martian analogue due to its structural similarities with Martian volcanoes. It lies to the SW of Almagro (38°49’13”N/3°44’37”W), within the Campo de Calatrava volcanic region in Spain [6], and is emplaced among Paleozoic host rocks where the Armorican quartzite yields the topographic heights.

Cerro Gordo is part of a volcanic lineation, all of olivinic nefelinite composition and thought to have erupted coevally (1.5 ± 0.3 Ma [7]), that follows a NNE-SSW fracture [8]. Its eruptive style varied with time from phreatomagmatic to strombolian and phreatomagmatic again to end with an effusive phase [9]. For this reason the deposits found in the field (pyroclastic surge deposits, lahar facies, scoria and pyroclastic deposits, a lava flow, tuffs, breccias and spatter deposits) are varied in composition and structure, and therefore comprise a large range of magnetic susceptibility values,  making Cerro Gordo an excellent scenario for a demonstration campaign of the susceptometer prototype.

2.2 Meteorites

A total of 16 meteorites of different compositions, and therefore varied susceptibility ranges, have been measured for this work, 10 aerolites and 6 siderites. The criteria followed was that their volume accomplished the minimum size stated in the introduction. The samples were divided into faces and measured twice in each of them. In the case of the siderites showing a flat polished face with Widmanstätten structures, the polished face was measured in two orthogonal directions to test the possible influence of the internal structural ordering.

• Conclusions

Previous results from Cerro Gordo showed the capability of the magnetic susceptibility results to distinguish between different rock deposits. The ongoing work on the collected samples analysis and geological description of the study location is intended to relate the magnetic susceptibility values with the mineral composition of the rocks, enhancing the comprehension of the susceptibility measurements and the structure of the volcano. The measurements on meteorites are currently under analysis, and aim to classify the measured samples as a function of their magnetic susceptibility [10].

Acknowledgements:

This work has been funded by the Spanish Programme for Research, Development and Innovation under the grants of references ESP2017-88930-R and PID2020-119208RB-I00: MagAres and MINOTAUR, respectively, as well as the European Union Project NEWTON, of grant agreement 730041. JSO is funded by the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement SIGMA no 893304.

 

References:

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[3] Rochette 2010, Earth Planet. Sci. Lett., 292: 383–391.

[4] Hunt et al. 2013, Wiley. Online Library. DOI: 10.1029/RF003p0189.

[5] Monasterio et al. 2021, Terrestrial Analogs Conference (LPI Contrib. No. 2595)

[6] Becerra-Ramírez et al. 2020, Geosciences, 10, 441.

[7] Ancoechea & Huertas 2021, J. Iberian Geology (47): 209-223.

[8] Ancoechea 1999, Enseñanza de las Ciencias de la Tierra (73): 237-243.

[9] González et al. 2010, Aportaciones Recientes en Volcanología 2005-2008: 57-65.

[10] Rochette et al. 2003, Meteoritics & Planet. Sci., 38: 251-268.