2001 Annual Science Report
NASA Jet Propulsion Laboratory Reporting | JUL 2000 – JUN 2001
Executive Summary — JPL (dm)
The JPL/Caltech node of the NAI has slowly evolved its scientific focus to be on the definition and detection of biosignatures that might be used to find evidence for extant or past life on Earth and on extraterrestrial environments, or within samples returned from such extraterrestrial sites. This evolution has occurred both in response to the members of our group expressing these interests, as well as the reviewers’ suggestions from the initial CAN application. The group includes members from a variety of research environments, including JPL, Caltech GPS (Geological and Planetary Sciences), University of Wisconsin (Geology), University of Rochester (Chemistry), USGS in Flagstaff, and the Carnegie Institution of Washington. The goals can be generally divided into three groups:
1. Stable isotopes of biosignatures:
a. nitrogen isotopes â?? Blake, Caltech
b. carbon and sulfur isotopes â?? Fogel and Rummel, Carnegie Inst. of Washington
c. iron isotopes â?? Beard and Johnson, Wisconsin
d. transition metal isotopes â?? Anbar, Univ. of Rochester
2. Reflectance spectroscopic biosignatures
a. large scale signatures in water bodies â?? USGS group
b. reflectance signatures in soils and rocks â?? Conrad, JPL
3. Life detection methodology â?? biosignature definition and measurement
a. definition of non-earthcentric biosignatures â?? Conrad & Nealson, JPL
b. UV fluorescence and Raman methods â?? Storrie-Lombardi et al., JPL
c. X-ray CT scanning methods â?? Tsapin, JPL
d. software development for life detection decision making and complexity analysis
e. study of extreme environments as analogues for extraterrestrial sites â?? Nealson, JPL
4. Metal oxide/organism interactions as biosignatures
a. magnetite as a biosignature â?? Kirschvink, Caltech
b. iron oxidizing bacteria, and low pH metal alteration â?? Banfield, Wisconsin
c. iron and manganese oxidizing and reducing bacteria â?? Nealson, JPL
The research focus is on microbiology, geomicrobiology, and the interactions between microbes and metals of different types. The work on stable isotopes has resulted in a number of advances in our thinking, especially in the area of stable isotopes of iron, but the work with sulfur, carbon, and nitrogen has also been very good. The work on iron isotopes is spearheaded by two groups, the Johnson/Beard group at Wisconsin, and the Anbar group at Rochester. While there is some disagreement between these two groups, both have published several articles on various aspects of iron fractionation, and the NAI effort in this area can be regarded as world-class. The acquisition of the NAI facility mass spec at U. of Wisconsin was a significant event, and has greatly aided in data availability by requiring smaller samples, speeding up the analysis time, and increasing the precision of the measurements.
One part of the biosignatures work, headed up by Gene McDonald (JPL), has been using amino acid ratios as indicators of life. This work has revealed two new and potentially very useful facts. First, amino acids (and their racemic signatures) are preserved for millions of years inside of Antarctic rocks where there are populations of endolithic bacteria near the surface. This allows one to not only estimate the amount of time that the rock has been populated, but would in principle allow one to identify a rock that had been, but was no longer populated by endolithic bacteria. Second, using amino acid racemization analyses, it has been possible to estimate the temperature history of some Arctic permafrost samples, something that has been very difficult to accomplish in the past.
The project on life detection methodology at JPL has emerged as one of importance. This project, led by Drs. Michael Storrie-Lombardi and Alexandre (Sasha) Tsapin, focuses on the use of two new technologies for the detection of potential life-containing strata. These two approaches (deep UV (224 nm) fluorescence, and CT X-ray scanning) have both yielded exceptional results, and are being prepared for publication now. Both of these projects have led to submission of instrument proposals to the ASTID program for flight instrument development.
Of particular note has been the work of Dr. J. Kirschvink, who has taken a strong stand on the issue of magnetite as a biosignature, and has published several abstracts and one paper strongly defending the idea that magnetite in the ALH84001 meteorite is an indicator of past life on Mars. This admittedly controversial stance has added an element of dynamics and tension to our already dynamic and tense NAI group!