Layered, massive and thin sediments on Mars: possible Late Noachian to Late Amazonian tephra?
Published:January 01, 2002
Mary G. Chapman, 2002. "Layered, massive and thin sediments on Mars: possible Late Noachian to Late Amazonian tephra?", Volcano–Ice Interaction on Earth and Mars, J. L. Smellie, M. G. Chapman
Download citation file:
Data from instruments on the currently orbiting Mars Global Surveyor (MGS) suggest that as an alternative interpretation to lacustrine deposits, widespread sediments on Mars may be tephra deposits of variable age, formed in part by volcano–ice interactions. The materials are often associated with outcrops of mapped geological units that have each been previously interpreted as volcanic ash deposits with identified, but unconfirmed possible volcanic vents. Spectral investigation indicates that although some outcrops are basaltic, many show moderate to high concentrations of andesite, a composition at which large explosive eruptions may be possible. In addition, many outcrops are in areas suspected to be water/ice rich. On Earth, magma and groundwater can react to create violent explosive eruptions. Observations from MGS support a pyroclastic mechanism of deposition and show some morphologies consistent with volcano–ice interactions, including subaqueous eruptions. Perhaps MGS data are finally producing more definitive evidence of the widespread tephra that were predicted to be likely in the reduced atmospheric pressure of Mars.
Figures & Tables
Volcano–Ice Interaction on Earth and Mars
This volume focuses on magmas and cryospheres on Earth and Mars and is the first publication of its kind to combine a thematic set of contributions addressing the diverse range of volcano-ice interactions known or thought to occur on both planets. Understanding those interactions is a comparatively young scientific endeavour, yet it is vitally important for a fuller comprehension of how planets work as integrated systems. It is also topical since future volcanic eruptions on Earth may contribute to melting ice sheets and thus to global sea level rise.
Papers included here are likely to influence the choice of sites for future Mars missions in exobiologically important areas. On Earth, snow and ice are widespread, not only in extensive icecaps but also as alpine glaciers at high elevations in tropical regions. By contrast, Mars today is an arid volcanic planet with only small polar ice-caps although an abundance of water is believed to be trapped in the cryolithosphere. It is also thought that the planet may have sustained extensive frozen oceans early in its history. The presence of a former hydrosphere, a cryosphere and coincident volcanism thus make Mars the likeliest prospect for the first discoveries of life away from Earth. Much research has assumed that terrestrial volcano-ice systems are plausible analogues for putative Martian examples, but until mankind finally sets foot on Mars, there is no simple test for that assumption.
Our hope is that the knowledge presented here will stimulate research among planetary geologists in this exciting, rapidly expanding field for many years to come.