An apparatus for simulating the environment at the surface of Mars has been developed. Within the apparatus, the pressure, gas composition, and temperature of the atmosphere; the incident solar visible and ultraviolet (UV) light; and the attenuation of the light by dust in the atmosphere can be simulated accurately for any latitude, season, or obliquity cycle over the entire geological history of Mars. The apparatus also incorporates instrumentation for monitoring chemical reactions in the simulated atmosphere. The apparatus can be used for experiments in astrobiology, geochemistry, aerobiology, and aerochemistry related to envisioned robotic and human exploration of Mars. Moreover, the apparatus can be easily adapted to enable similar experimentation under environmental conditions of (1) the surfaces of moons, asteroids, and comets, and (2) the upper atmospheres of planets other than Mars: in particular, it can be made to simulate conditions anywhere in the terrestrial atmosphere at altitudes up to about 100 km.

This Laboratory Apparatus reproduces, inside the chamber, environmental conditions like those on the Martian surface or in the upper terrestrial atmosphere.
The apparatus (see figure) includes a cylindrical stainless-steel chamber, wherein the simulated atmospheric pressure is maintained between set points by means of a vacuum pump and a throttle valve controlled by an electronic pressure controller. The pressure can be set at any level from ambient down to 0.1 mb (100 Pa). A commercially available Martian-atmosphere-simulating mixture of gases (95.54% CO2 + 2.7% N2 + 1.6% Ar + 0.13% O2 + 0.03% H2O) is delivered from a tank to the chamber through a mass-flow controller. The primary temperature-control system is a commercially available unit that includes a cold plate in the chamber and that utilizes liquid nitrogen to reach the lowest temperatures. The temperature-control system can be programmed to maintain any temperature between –100 and +160 °C and/or to impose diurnal heating and cooling cycles.

Ultraviolet (UV), visible (VIS), and near-infrared light (IR) are supplied to the inside of the chamber through fused-silica glass ports. In the original Mars version of the apparatus, the UV light is generated by a xenon-arc lamp and can be adjusted to any realistic current or ancient Martian UV flux density. To suppress spurious thermal IR radiation, a water filter between the xenon-arc lamp and the chamber attenuates near- and mid-infrared light. The light-attenuating effects of dust in the atmosphere are simulated by means of a series of neutral-density filters, ranging from an optical depth of 0.1 (representing a dust-free sky) to an optical depth of 3.5 (representing a global dust storm).

This work was done by Andrew C. Schuerger of the University of Florida for Kennedy Space Center. KSC-13190

Topics:
Physical Sciences Pressure Sun and solar Vacuum Water
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NASA Tech Briefs Magazine

This article first appeared in the August, 2009 issue of NASA Tech Briefs Magazine (Vol. 33 No. 8).

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