Christopher P. McKay

Signatures of Habitats and Life in Earth’s High-Altitude Lakes: Clues to Noachian Aqueous Environments on Mars

14.1 IntroductionA series of astrobiological high-altitude expeditions to the South AmericanAndean Mountains were initiated in 2002 to explore the highest perenniallakes on Earth, including several volcanic crater lakes at or above 6000 min elevation. During the next five years, they will provide the first integratedlong-term astrobiological characterization and monitoring of lacustrineenvironments and their biology at such an altitude. These extreme lakesare natural laboratories that provide the field data, currently missingabove 4000 m, to complete our understanding of terrestrial lakes and biota.Research is being performed on the effects of UV in low-altitude lakesand models of UV flux over time have been developed (Cockell, 2000). Thelakes showing a high content of dissolved organic material (DOM) shieldorganisms from UV effects (McKenzie et al., 1999; Rae et al., 2000). DOMacts as a natural sunscreen by influencing water transparency, and thereforeis a determinant of photic zone depth (Reche et al., 2000). In sparselyvegetated alpine areas, lakes tend to be clearer and offer less protectionfrom UV to organisms living in the water. Transparent water, combinedwith high UV irradiance may maximize the penetration and effect of UVradiation as shown for organisms in alpine lakes (e.g., Vincent et al., 1984;Vinebrook and Leavitt, 1996). Shallow-water benthic communities in theselakes are particularly sensitive to UV radiation. Periphyton, which definescommunities of microorganisms in bodies of water, can live on varioussusbtrates. While on rocks, they include immobile species that cannot seeklow UV refuges unlike sediment-dwelling periphyton (Happey-Wood, 1988;Vincent et al., 1993) or alpine phytoflagellates (Rott, 1988) which bothundergo vertical migration. Inhibition of algal photosynthesis by UV radia-tion has been documented in the laboratory (Ha ¬der, 1993) and it has beenshown that phytoplankton production is reduced by formation of nucleic acidlesions (Karentz et al., 1991) or production of peroxides and free oxygenradicals (Cooper et al., 1989). Most of the experiments that have demon-strated in situ suppression of algal growth by UV radiation have eitherused artificially enhanced UV irradiance (Worrest et al., 1978) or shallowsystems (<1 cm) that lack significant natural attenuation of UV radiation(Bothwell et al., 1993, 1994). Our project is providing the field data thatare missing from natural laboratories above 4000 m and will complementthe postulation of the effects of UV on life and its adaptation modes(or lack thereof).The exploration of high-altitude lakes could shed light on early EarthOsbiological evolution as well. For two billion years, EarthOs atmosphere

Subsurface ice and brine sampling using an ultrasonic/sonic gopher for life detection and characterization in the McMurdo Dry Valleys

There is growing evidence for ice and fluids near the surface of Mars with potential discharge of brines, which may preserve a record of past life on the planet. Proven techniques to sample Mars subsurface will be critical for future NASA astrobiology missions that will search for such records. The required technology studies are underway in the McMurdo Dry valleys, Antarctica, which is serving as a Mars analog. The ice layer on Lake Vida in the dry valleys is estimated to be 20-meter thick where below 16-m depth there is a mix of ice and brine, which has never been sampled directly due to logistical constraints. A novel light weight, low power ultrasonic/sonic driller/corer (USDC) mechanism was developed that overcomes the need for high axial loads required by drilling via conventional techniques. The USDC was modified to produce an Ultrasonic/Sonic Gopher that is being developed to core down to the 20-m depth for in situ analysis and sample collection. Coring ice at -20°C as in Lake Vida suggests that it is a greater challenge and current efforts are focused on the problems of ice core cutting, ice chip handling and potential ice melt (and refreezing) during drilling. An analytical model and a prototype are being developed with an effort to optimize the design while addressing the thermal issues, drilling rate, power, mass and the electromechanical behavior.

Testing of a 1 meter Mars IceBreaker Drill in a 3.5 meter Vacuum Chamber and in an Antarctic Mars Analog Site

In this paper we report on the development of a rotary-percussive sampling drill: the IceBreaker. The purpose of the drill is to penetrate at least 1 meter in icy-regolith and in ice, and acquire sub-surface sample for science analysis. The drill was tested at a Mars analog site in the Dry Valleys of Antarctica and inside a 3.5 meter vacuum chamber in icy-soil, ice and ice with 2% perchlorate. In all cases, the drill reached ~1 meter depth in approximately one hour. The average power was 100 Watts and Weight on Bit was less than 100 Newton. This corresponds to the drilling energy of 100 Whr. In each case approximately 500 cubic centimeters of sample was recovered and deposited into sterile bags.

Noctilucent cloud formation and the effects of water vapor variability on temperatures in the middle atmosphere

Abstract To investigate the occurrence of low temperatures and the formation of noctilucent clouds in the summer mesosphere a one-dimensional time-dependent photochemical-thermal numerical model of the atmosphere between 50 and 120 km has been constructed. The model includes the important chemistry of the hydrogen and oxygen species and transport by eddy and molecular processes. The thermal balance incorporates: heating by solar ultraviolet radiation; transport of chemical potential energy; eddy diffusion and dissipation; molecular conduction; airglow emissions; and infrared cooling by carbon dioxide. A non- LTE parameterization is used to calculate 15 μm band cooling by carbon dioxide. The model self-consistently solves the coupled photochemical and thermal equations as perturbation equations from a reference state assumed to be in equilibrium and is used to consider the effect of variability in water vapor in the lower mesosphere on the temperature in the region of noctilucent cloud formation. It is found that change in water vapor from an equilibrium value of 5 ppm at 50 km to a value of 10 ppm, a variation consistent with observations, can produce a ~ 15 K drop in temperature at 82 km. It is suggested that this process may produce long periods (weeks) of cold temperatures and influence noctilucent cloud formation.

The case for human exploration of Mars

The results of a workshop on the feasibility and logic of a manned Mars mission and base are discussed. Criteria for evaluating the merit of proposed Mars expeditions are presented, and the precursor mission requirements of various proposed scenarios are considered. Science objectives and how various mission scenarios would serve them are addressed. Issues of launch, assembly, transportation, and Mars base infrastructure are examined. Advanced propulsion concepts for use in a Mars mission are discussed, and international cooperation in a Mars mission is addressed. The relevance of the workshop to the crisis of education in America is considered.

Habitability and Biomarker Preservation in the Martian Near-Surface Radiation Environment

Abstract Numerical models and measurements at the Martian surface show that ionizing radiation in the form of galactic cosmic rays and solar energetic particles impinging on the planets surface and results in the formation of secondary ionizing radiation that affects the top dozen meters of the subsurface. In this brief review, we quantitatively model this secondary ionizing radiation as function of energy and depth. We then use basic physical arguments to explain the effect of this secondary ionization on organic molecules and cells and estimate microbe survival times as function of depth and soil type. Finally, we compare our calculated results on Deinococcus radiodurans survival time with other studies that have been reported in the literature.

Investigating Fluidized Granular Flow Behavior in Extraterrestrial Environments for a Pneumatic Regolith Acquisition System

Keeping in mind the enormous scientific benefits of bringing extraterrestrial samples back to Earth, efforts are undertaken to improve the performance of Honeybee Robotics’ Pneumatic Regolith Acquisition System: PLANETVAC. Positive pressure pneumatic conveying systems rely on complex layouts for particle transport and require efficient designs. For it to function with redundancy and without human interaction in extraterrestrial environments, it becomes imminent to model gas-solid flow behavior and put forth critical findings. There has yet to be a comprehensive study of fluidized granular flow in reduced (or zero) gravity environments to better assist design of EVA/ ISRU equipment for future missions. These findings shall induce design adjustments that will improve gasregolith mixing for efficient transport of the samples under Martian conditions. A critical area to model the flow is the “pneumatic injectionMartian Surface regolith zone”. Effects of pneumatic injection velocity vectors upon regolith volume fraction distribution and subsequent transport within the system is studied within a cylindrical pipe with inlets for gas injection onto the exposed regolith surface area. Key gas nozzle design variations are modeled and tested for appreciation of captured regolith mass. Swirl motion of gases have shown to impart higher momenta per square millimeter as compared to direct downward injection of gas. An increasing trend of injection angle shows a wider and uniform distribution of sand volume fraction, signifying a higher lift of sand particles.