Simulating physical weathering of basalt on Earth and Mars

Viles, HA; Ehlmann, BL; Cebula, Tomasz; Wilson, Colin; Mol, Lisa; Bourke, MC

Abstract

Background
Despite its importance as a surficial rock type on Earth and other planets, few studies have been made of the response of basalt to physical weathering. Heating and cooling, with or without salts and moisture, may have severe impacts on basalt clasts in many extreme environments (Leask & Wilson, 2003). We report here on an integrated programme of simulations investigating physical weathering of basalt under Earth (hot desert) and Mars conditions using a Fison’s Environmental Cabinet and a specially constructed Mars Environment Simulation Chamber.

Methods
Small blocks (9 x 2.3 x 2.5 cm) of basalt were cut, and two groups prepared: (1) thermally pre-stressed and (2) thermally pre-stressed and immersed in saturated Na2SO4 solution. Sample strength was assessed before and after experimental weathering using a Grindosonic, and thin sections were produced for detailed petrological examination. Ambient, block surface and internal temperatures were monitored throughout the experiments. The Earth weathering regime was set up to reflect Negev desert conditions cycling between 296K and 345K; whilst the Martian regime cycled from 190K to 277K. Cycle length was 8 hrs. in each case. Both weathering regimes also included an element of radiative heating via lamps coming on for part of the heating cycle. The Mars weathering regime was carried out in 100% CO2 atmosphere at 9 mbar pressure.

Results and conclusions
After 36 cycles under Earth and Mars conditions, changes in strength (few %) were apparent and some microscopic cracking was observed, although no visible weathering was produced. Blocks subjected to Mars-like conditions reacted differently to those subjected to Negev desert conditions especially with regard to whether salts caused strengthening or weakening.

References
Leask, HJ and Wilson, L. (2003) Heating and cooling of
rocks on Mars: Consequences for weathering. Lunar and
Planetary Science Conference 34, abstract 1320.pdf

• Presentation Conference Type: Conference Paper (unpublished)
• Conference Name: Goldschmidt Conference
• Start Date: Aug 19, 2007
• End Date: Aug 24, 2007
• Acceptance Date: May 1, 2007
• Publication Date: Aug 24, 2007
• Deposit Date: Dec 14, 2016
• Publicly Available Date: Dec 14, 2016
• Peer Reviewed: Peer Reviewed
• Keywords: basalt, rock, Mars, Earth, weathering, heat, desert
• Public URL: https://uwe-repository.worktribe.com/output/1025870
• Publisher URL: https://goldschmidt.info/2007/abstracts/UV.pdf
• Additional Information: Title of Conference or Conference Proceedings : Goldsmiths Conference Abstracts 2007
• Contract Date: Dec 14, 2016