Publication
- Names
-
- Boris Chauviré
- Maxime Pineau
- Eric Quirico
- Pierre Beck
- Title
- Near infrared signature of opaline silica at Mars-relevant pressure and temperature
- Abstract
- Opal is a mineral of great interest for tracing the aqueous Mars’ history. Detection of opal on Mars is based on the near infrared absorption bands attributed to its content in water and hydroxyl. However, pressure and temperature can affect the amount and configuration of water in hydrated minerals, and consequently the associated absorption bands. Here, we investigate the effects of Mars atmospheric relevant pressure and temperature on opal’s NIR signature. By exposing opal samples at 1 to 8 mbar, and between -27 and -52°C, we simulate the conditions experienced by opaline silica on Mars surface. We demonstrate that opal releases molecular water at low pressure, inducing changes on all bands, as observed by previous studies. However, we observe that this dehydration is not systematic (six opals among thirteen). Exposed to low temperature, water molecules in opal crystallize, inducing significant variation in shape and position of the bands at 5200 cm-1 and 7000 cm-1 (1.9 μm and 1.4 μm respectively). Low temperature experiments demonstrate that opal, and particularly opal-CT, could have a spectral signature very similar to water ice. These experimental data are compared with silica signature detected on Mars by CRISM and we show that martian opaline silica have signature specific of water ice, notably a shoulder near 5100 cm-1 (1.96 μm). We show that opal can retain water under martian conditions, water that can be trapped since its precipitation.
- Keywords
- spectroscopy, near-IR, data analysis, transmission
- Content
- spectral data, planetary sciences
- Year
- 2021
- Journal
- Earth and Planetary Science Letters
- Volume
- 576
- Pages
- 117239
- Pages number
- 13
- Document type
- article
- Publication state
- published