Characterization of Biosignatures within Geologic Samples Analyzed using a Suite of in situ Techniques
Kyle Uckert, NMSU
I investigated the biosignature detection capabilities of several in situ techniques to evaluate their potential to
detect the presence of extant or extinct life on other planetary surfaces. These instruments included: a laser desorption
time-of- flight mass spectrometer (LD-TOF-MS), an acousto-optic tunable filter (AOTF) infrared (IR) point spectrometer, a
laser-induced breakdown spectrometer (LIBS), X-ray diffraction (XRD)/X-ray fluorescence (XRF), and scanning electron
microscopy (SEM)/energy dispersive X-Ray spectroscopy (EDS). I measured the IR reflectance spectra of several speleothems
in caves in situ to detect the presence of biomineralization. Microorganisms (such as those that may exist on other solar
system bodies) mediate redox reactions to obtain energy for growth and reproduction, producing minerals such as
carbonates, metal oxides, and sulfates as waste products. Microbes occasionally become entombed in their mineral
excrement, essentially acting as a nucleation site for further crystal growth. This process produces minerals with a
crystal lattice distinct from geologic precipitation, detectable with IR reflectance spectroscopy. Using a suite of
samples collected from three subterranean environments, along with statistical analyses including principal component
analysis, I measured subsurface biosignatures associated with these biomineralization effects, including the presence of
trace elements, morphological characteristics, organic molecules, and amorphous crystal structures.
I also explored the optimization of a two-step LD-TOF-MS (L2MS) for the detection of organic molecules and other
biosignatures. I focused my efforts on characterizing the L2MS desorption IR laser wavelength dependence on organic
detection sensitivity in an effort to optimize the detection of high mass (≤100 Da) organic peaks. I analyzed samples
with an IR reflectance spectrometer and an L2MS with a tunable desorption IR laser whose wavelength range (2.7 – 3.45
microns) overlaps that of our IR spectrometer (1.6 – 3.6 microns), and discovered a IR resonance enhancement effect. A
correlation between the maximum IR absorption of organic functional group and mineral vibrational transitions – inferred
from the IR spectrum – and the optimal IR laser configuration for organic detection using L2MS indicates that IR
spectroscopy may be used to inform the optimal L2MS IR laser wavelength for organic detection. This work suggests that a
suite of instruments, particularly LD-TOF-MS and AOTF IR spectroscopy, has strong biosignature detection potential on a
future robotic platform for investigations of other planetary surfaces or subsurfaces.
The NMSU Department of Astronomy will hold an observatory open house at the NMSU campus observatory at 8 p.m.Friday, Sept. 9. Astronomy personnel on hand will be Chris Churchill and graduate assistants Xander Thelen, Trevor Picard and Jacob Vander Vliet.
Guests can view Mars and Saturn together in the evening sky in the constellation of Scorpio. Telescopes will also have the center of the Milky Way Galaxy in view, and in this region there are many beautiful star clusters and globular clusters (tight groups of millions of stars). High in the sky, viewers will see the constellation Vega with its double-double star system and the famous ring nebula, which is the remnants of a dying star much like our own sun. The moon will be in the phase called first quarter and will make a wonderful sight.
Contact the NMSU Astronomy Department at 575-646-4438 with questions. Everyone is welcome to come and spend an evening of stargazing. Admission is free and children are especially welcome to attend.
For information on what is up in September, go here: http://whatsouttonight.com/Resources/2016SepSkyWOT.pdf
A .pdf of the talk can be found here.
Observations of Solar System Bodies with the VLA and ALMA
Dr. Bryan Butler, NRAO
Observations of solar system bodies at wavelengths from submm to meter wavelengths provide important and unique information about those bodies. Such observations probe to depths unreachable at other wavelengths – typically of order 10-20 wavelengths for bodies with solid surfaces, and as deep as tens of bars for those with thick atmospheres (the giant planets). In the past five years, two instruments have been commissioned which have revolutionized the ability to make very sensitive, high-resolution observations at these wavelengths: the Karl G. Jansky Very Large Array (VLA) and the Atacama Large Millimeter/Submillimeter Array (ALMA). I will present a discussion of results over the past five years from observations from both the VLA and ALMA. These include observations of the atmospheres of all of the giant planets, the rings of Saturn, and the surfaces of many icy bodies in the outer solar system. I will also present plans for the Next Generation Very Large Array (ngVLA), the next step for millimeter to centimeter wavelength interferometry.
Cosmology from the Moon: The Dark Ages Radio Explorer (DARE)
Dr. Jack Burns, University of Colorado Boulder
In the New Worlds, New Horizons in Astronomy & Astrophysics Decadal Survey, Cosmic Dawn was singled out as one of the top astrophysics priorities for this decade. Specifically, the Decadal report asked “when and how did the first galaxies form out of cold clumps of hydrogen gas and start to shine—when was our cosmic dawn?” It proposed “astronomers must now search the sky for these infant galaxies and find out how they behaved and interacted with their surroundings.” This is the science objective of DARE – to search for the first stars, galaxies, and black holes via their impact on the intergalactic medium (IGM) as measured by the highly redshifted 21-cm hyperfine transition of neutral hydrogen (HI). DARE will probe redshifts of 11-35 (Dark Ages to Cosmic Dawn) with observed HI frequencies of 40-120 MHz. DARE will observe expected spectral features in the global signal of HI that correspond to stellar ignition (Lyman-α from the first stars coupling with the HI hyperfine transition), X-ray heating/ionization of the IGM from the first accreting black holes, and the beginning of reionization (signal dominated by IGM ionization fraction). These observations will complement those expected from JWST, ALMA, and HERA. We propose to observe these spectral features with a broad-beam dipole antenna along with a wide-band receiver and digital spectrometer. We will place DARE in lunar orbit and take data only above the farside, a location known to be free of human-generated RFI and with a negligible ionosphere. In this talk, I will present the mission concept including initial results from an engineering prototypes which are designed to perform end-to-end validation of the instrument and our calibration techniques. I will also describe our signal extraction tool, using a Markov Chain Monte Carlo technique, which measures the parameterized spectral features in the presence of substantial Galactic and solar system foregrounds.
Giant Planet Shielding of the Inner Solar System Revisited: Blending Celestial Mechanics with Advanced Computation
Dr. William Newman, UCLA
The Earth has sustained during the last billion years as many as five catastrophic collisions with asteroids and comets which led to widespread species extinctions. Our own atmosphere was literally blown away 4.5 billion years ago by a collision with a Mars-sized impactor. However, collisions with comets originating in the outer solar system accreted much of the present-day atmosphere. Relatively advanced life on our planet is the beneficiary of a number of impact events during Earth’s history which built our atmosphere without destroying a large fraction of terrestrial life. Using very high precision Monte Carlo integration methods to explore the orbital evolution over hundreds of millions of years followed by the application of celestial mechanical techniques, the presentation will explain directly how Earth was shielded by the combined influence of Jupiter and Saturn, assuring that only 1 in 100,000 potential collisions with the Earth will materialize.
Clues to Globular Cluster Formation
David Nataf, Johns Hopkins University
Globular clusters are now well-established to host “Second-generation” stars, which show anomalous abundances in some or all of He, C, N, O, Na, Al, Mg, etc. The simplest explanations for these phenomena typically require the globular clusters to have been ~20x more massive at birth, and to have been enriched by processes which are not consistent with the theoretical predictions of massive star chemical synthesis models. The library of observations is now a vast one, yet there has been comparatively little progress in understanding how globular clusters could have formed and evolved. In this talk I discuss two new insights into the matter. First, I report on a meta-analysis of globular cluster abundances that combined APOGEE and literature data for 28 globular clusters, new trends with globular cluster mass are identified. I discuss the chemical properties of former globular cluster stars that are now part of the field population, and what can be learned.
Solving the Puzzles of the Moon
Shun Karato, Yale University
After 50 years from the first landing of men on the Moon, about 380 kg of samples were collected by the Apollo mission. Chemical analyses of these samples together with a theory of planetary formation led to a “giant impact” paradigm (in mid 1970s). In this paradigm, the Moon was formed in the later stage of Earth formation (not the very late stage, though), when the proto-Earth was hit by an impactor with a modest size (~ Mars size) at an oblique angle. Such an impact is a natural consequence of planetary formation from a proto-planetary nebula. This collision may have kicked out mantle materials from the proto-Earth to form the Moon. This model explains mostly rocky composition of the Moon and the large angular momentum of the Earth-Moon system. High temperatures caused by an impact likely removed much of the volatile components such as water.
However, two recent geochemical observations cast doubt about the validity of such a paradigm. They include (i) not-so-dry Moon suggested from the analysis of basaltic inclusions in olivine, and (ii) the high degree of similarities in many isotopes. The first observation is obviously counter-intuitive, but the second one is also hard to reconcile with the standard model of a giant impact, because many models show that a giant impact produces the Moon mostly from the impactor. In this presentation, I will show how one can solve these puzzles by a combination of physics/chemistry of materials with some basic physics of a giant impact.