Time filter

Source Type

Mountain View, CA, United States

Fairen A.G.,Search for Extraterrestrial Intelligence Institute
Nature Geoscience | Year: 2010

The northern plains of Mars are thought to have harboured an ocean more than 3.6 billion years ago. Delta deposits and river-valley termini ring the proposed seabed and define an equipotential palaeoshoreline. © 2010 Macmillan Publishers Limited. All rights reserved.

Jenniskens P.,Search for Extraterrestrial Intelligence Institute
Journal of Spacecraft and Rockets | Year: 2010

Spectroscopic observations of the 2006 Stardust Sample Return Capsule entry are presented, obtained by means of a slitless miniature echelle spectrograph onboard NASA's DC-8 airborne laboratory. The data cover the wavelength range from 336 to 880 nm, at 0.14-0.9 nm resolution, and were obtained during the time interval when radiative heating was most important. The data contain a broadband continuum, presumably from the hot heat-shield surface, shock-layer air plasma emissions of N, O, and N2, and atomic hydrogen and CN molecular band emission from the ablating heat-shield material, a form of phenol-impregnated carbon ablator. Early in flight, there were also atomic line emissions of Zn, K, Ca+, and Na, presumably from a white Z-93P paint applied to the top of the phenol- impregnated carbon ablator. At each moment along the trajectory, the whole spectrum was recorded simultaneously, but broken into smaller segments. Key issues addressed in the data reduction and calibration are described. The interpretation of these data was given elsewhere.

Huang X.,Search for Extraterrestrial Intelligence Institute | Fortenberry R.C.,NASA | Lee T.J.,NASA
Astrophysical Journal Letters | Year: 2013

Very recently, molecular rotational transitions observed in the photon-dominated region of the Horsehead nebula have been attributed to l-C3H+. In an effort to corroborate this finding, we employed state-of-the-art and proven high-accuracy quantum chemical techniques to compute spectroscopic constants for this cation and its isotopologues. Even though the B rotational constant from the fit of the observed spectrum and our computations agree to within 20 MHz, a typical level of accuracy, the D rotational constant differs by more than 40%, while the H rotational constant differs by three orders of magnitude. With the likely errors in the rotational transition energies resulting from this difference in D on the order of 1 MHz for the lowest observed transition (J = 4 → 3) and growing as J increases, the assignment of the observed rotational lines from the Horsehead nebula to l-C3H+ is questionable. © 2013. The American Astronomical Society. All rights reserved..

Bauschlicher Jr. C.W.,NASA | Ricca A.,Search for Extraterrestrial Intelligence Institute
Astrophysical Journal | Year: 2013

The loss of one hydrogen from C96H24 does not significantly affect the infrared spectra of the neutral, cation, or anion. Excluding a very weak C-C stretching band at 5.1 μm, the loss of two adjacent duo hydrogens does not significantly affect the spectra compared with the parent. Removing all of the hydrogen atoms significantly increases the intensity of the new C-C stretching band, and, for the cation, shifts it to a longer (5.2 μm) wavelength. Observations show a feature near 5.25 μm, which has been attributed to overtone and combination bands from polycyclic aromatic hydrocarbons (PAHs). This current work suggests that dehydrogenated PAHs might also contribute to this band, but its weakness implies that fully dehydrogenated cationic or dicationic species are very rare. © 2013. The American Astronomical Society. All rights reserved.

Horneck G.,German Aerospace Center | Klaus D.M.,University of Colorado at Boulder | Mancinelli R.L.,Search for Extraterrestrial Intelligence Institute
Microbiology and Molecular Biology Reviews | Year: 2010

The responses of microorganisms (viruses, bacterial cells, bacterial and fungal spores, and lichens) to selected factors of space (microgravity, galactic cosmic radiation, solar UV radiation, and space vacuum) were determined in space and laboratory simulation experiments. In general, microorganisms tend to thrive in the space flight environment in terms of enhanced growth parameters and a demonstrated ability to proliferate in the presence of normally inhibitory levels of antibiotics. The mechanisms responsible for the observed biological responses, however, are not yet fully understood. A hypothesized interaction of microgravity with radiation-induced DNA repair processes was experimentally refuted. The survival of microorganisms in outer space was investigated to tackle questions on the upper boundary of the biosphere and on the likelihood of interplanetary transport of microorganisms. It was found that extraterrestrial solar UV radiation was the most deleterious factor of space. Among all organisms tested, only lichens (Rhizocarpon geographicum and Xanthoria elegans) maintained full viability after 2 weeks in outer space, whereas all other test systems were inactivated by orders of magnitude. Using optical filters and spores of Bacillus subtilis as a biological UV dosimeter, it was found that the current ozone layer reduces the biological effectiveness of solar UV by 3 orders of magnitude. If shielded against solar UV, spores of B. subtilis were capable of surviving in space for up to 6 years, especially if embedded in clay or meteorite powder (artificial meteorites). The data support the likelihood of interplanetary transfer of microorganisms within meteorites, the so-called lithopanspermia hypothesis. Copyright © 2010, American Society for Microbiology. All Rights Reserved.

Discover hidden collaborations