Evidence about hydrate and solid water in the Martian surface from the 1969 Mariner Infrared Spectrometer

Abstract

The Mariner Mars 6 and 7 infrared spectrometer spectra of Mars include a broad absorption near 3 μ that can be ascribed to water of hydration in the surface minerals and/or ice. Laboratory experiments show that an increase in either form of condensed phase water is accompanied by a decreased intensity ratio R1 = I(3.10 μ)/I(2.20 μ). Evidence for the presence of ice is provided by the intensity ratio R2 = I(2.90 μ)/I(3.10 μ) since R2 is below unity for silicate hydrates and exceeds unity for ice. Near the Martian equator both the surface temperature and R1depend inversely upon brightness at 2.2 μ: a doubling of B(2.2 μ) is accompanied by a 19° temperature drop and a 30% drop in R1. BothR1 and R2 depend upon latitude: R1 is low near the equator and at latitudes more southerly than 50°S, whereas R1 is high in between. These data show that condensed phase water is present throughout the observed surface of Mars, the brighter areas near the equator (and north of it) and the regions south of 50°S being the most hydrated. All three variables, B(2.2), R1, and R2, change dramatically and in concert in a 5° latitude range at the polar cap edge. The characteristic spectral signature of ice can be discerned as well, indicating that ice is forming in this region, most likely on the planetary surface.

Multiple techniques for mineral identification on Mars:

“…This lab study is only a beginning; these studies need to be performed on a broader range of samples in the lab and in the field. Remote sensing of Mars has included thermal-IR spectrometers on the Mariner missions (Hanel et al, 1972;Pimentel et al, 1974), the TES on Mars Global Surveyor (Christensen et al, 2001b) and THEMIS on Mars Odyssey (Christensen et al, 2003), as well as VNIR telescopic and orbiter measurements (Adams and McCord, 1969;McCord et al, 1982;Bell et al, 1990;Bibring et al, 1990;Erard et al, 1991;Murchie et al, 2000). Typically these datasets have been analyzed in isolation because of the lack of correlated lab and field studies and because of the lack of spatial overlap on Mars.…”

Spectroscopic and geochemical analyses of ferrihydrite from springs in Iceland and applications to Mars

“…30 km spatial resolution achieved by the infrared spectrometers on Mariner 6 and 7 (e.g. Pimentel et al 1974). Still, the spatial resolution of TES would not be expected to allow detection of the c. 1400 and 1500 cm -1 bands.…”

Near-Infrared Spectral Variations of Martian Surface Materials from ISM Imaging Spectrometer Data

“…The crystalline phase is widely thought to be hematite (Adams and McCord 1969, McCord et al 1977, 1982, Singer et al 1979, Morris et al 1989, Bell et al 1990, Bell 1992. At near-infrared (NIR) wavelengths, a strong absorption at 3 µm shows that some molecular water is present, probably bound as mineral hydrates (Moroz 1964, Houck et al 1973, Pimental et al 1974. Absorptions due to silicates in the dust are weakly defined at best, suggesting poorly crystalline materials.…”