Encrenaz T.,University Paris Diderot |
Greathouse T.K.,SWRI |
Roe H.,Lowell Observatory |
Richter M.,University of California at Davis |
And 4 more authors.
Astronomy and Astrophysics | Year: 2012
We have been using the TEXES high-resolution imaging spectrometer at the NASA Infrared Telescope Facility to map sulfur dioxide and deuterated water over the disk of Venus. Observations took place on January 10-12, 2012. The diameter of Venus was 13 arcsec, with an illumination factor of 80%. Data were recorded in the 1344-1370 cm -1 range (around 7.35 μm) with a spectral resolving power of 80 000 and a spatial resolution of about 1.5 arcsec. In this spectral range, the emission of Venus comes from above the cloud top (z = 60-80 km). Four HDO lines and tens of SO 2 lines have been identified in our spectra. Mixing ratios have been estimated from HDO/CO 2 and SO 2/CO 2 line depth ratios, using weak neighboring transitions of comparable depths. The HDO maps, recorded on Jan. 10 and Jan. 12, are globally uniform with no significant variation between the two dates. A slight enhancement of the HDO mixing ratio toward the limb might be interpreted as a possible increase of the D/H ratio with height above the cloud level. The mean H 2O mixing ratio is found to be 1.5 0.75 ppm, assuming a D/H ratio of 0.0312 (i.e. 200 times the terrestrial value) over the cloud deck. The SO 2 maps, recorded each night from Jan. 10 to Jan. 12, show strong variations over the disk of Venus, by a factor as high as 5 to 10. In addition, the position of the maximum SO 2 mixing ratio strongly varies on a timescale of 24 h. The maximum SO 2 mixing ratio ranges between 75 25 ppb and 125 50 ppb between Jan. 10 and Jan. 12. The high variability of sulfur dioxide is probably a consequence of its very short photochemical lifetime. © 2012 ESO.
Encrenaz T.,LESIA |
Greathouse T.K.,SWRI |
Lefevre F.,French National Center for Scientific Research |
Atreya S.K.,University of Michigan
Planetary and Space Science | Year: 2012
Ever since the Viking mass spectrometer failed to detect organics on the surface of Mars in 1976 (Biemann et al.; 1976), hydrogen peroxide (H 2O 2) has been suggested as a possible oxidizer of the Martian surface (Oyama and Berdahl, 1977). However, the search for H 2O 2 on Mars was unsuccessful for three decades. In 2003, hydrogen peroxide was finally detected using two ground-based independent techniques, first with submillimeter heterodyne spectroscopy (Clancy et al.; 2004) and then again with thermal infrared imaging spectroscopy (Encrenaz et al.; 2004). The latter method has been used to simultaneously monitor the abundances and spatial distributions of H 2O 2 and H 2O on Mars as a function of the seasonal cycle. Comparison with the LMD Global Climate Model (GCM) shows that the observations favor simulations taking into account heterogeneous chemistry (Lefèvre et al.; 2008). It has been suggested (Delory et al.; 2006; Atreya et al.; 2006, 2007) that large amounts of hydrogen peroxide could be generated by triboelectricity during dust storms or dust devils. This paper presents a review of the present H 2O 2 dataset and an analysis of observability of peroxide during such events using present and future means. © 2011 Elsevier Ltd.
Johnson R.E.,University of Virginia |
Johnson R.E.,New York University |
Oza A.,University of Virginia |
Oza A.,University Pierre and Marie Curie |
And 3 more authors.
Astrophysical Journal | Year: 2015
Observations indicate that some of the largest Kuiper Belt Objects (KBOs) have retained volatiles in the gas phase (e.g., Pluto), while others have surface volatiles that might support a seasonal atmosphere (e.g., Eris). Since the presence of an atmosphere can affect their reflectance spectra and thermal balance, Schaller & Brown examined the role of volatile escape driven by solar heating of the surface. Guided by recent simulations, we estimate the loss of primordial N2 for several large KBOs, accounting for escape driven by UV/EUV heating of the upper atmosphere as well as by solar heating of the surface. For the latter we present new simulations and for the former we scale recent detailed simulations of escape from Pluto using the energy limited escape model validated recently by molecular kinetic simulations. Unlike what has been assumed to date, we show that unless the N2 atmosphere is thin (<∼1018 N2 cm-2) and/or the radius small (<∼200-300 km), escape is primarily driven by the UV/EUV radiation absorbed in the upper atmosphere. This affects the discussion of the relationship between atmospheric loss and the observed surface properties for a number of the KBOs examined. Our long-term goal is to connect detailed atmospheric loss simulations with a model for volatile transport for individual KBOs. © 2015. The American Astronomical Society. All rights reserved..
Agency: Department of Defense | Branch: Army | Program: STTR | Phase: Phase II | Award Amount: 749.37K | Year: 2008
Early detection of corrosion or the advent of corrosive environments in nominally protected assets, and monitoring its extent can help control corrosion initiated failures and predict the degradation or useful remaining life of utility pipeline infrastructure. Although preventive maintenance and periodic visual inspections are utilized to monitor damage and assess costs of corrosion, an autonomous monitoring system is desired to reduce maintenance costs and improve monitoring efficiency. An integrated sensor suite that measures true corrosion rates, corrosive damage or corrosivity autonomously and in real-time communicate this information to an analysis hub is being proposed here.
Between our physical exploration of the extremes of Earth's geography and environment, the solar system, and our great astronomical devices, humans have become used to a certain intimacy with the near and far universe. But it's not always easy to pinpoint what you're looking at when pictures are shown out of context. Here's a brief challenge for you: Can you identify the following images? If so you've definitely earned your cosmic merit badge. [Answers and image credits are at the end of this post] (1) Large (over 150 micron) Martian sand-grains after sifting by the Curiosity rover. Image about an inch square. Credit: NASA/JPL-Caltech/MSSS. (2) Part of a solar filament (dark) breaking away from the Sun in 2015, seen in extreme ultraviolet light where the filament plasma appears cooler and darker. Spotted by the SOHO's C2 coronograph. Credit: NASA/SOHO. (3) Part of the image of a distant galaxy being gravitationally lensed by a foreground massive galaxy, image taken by the Hubble Space Telescope. Credit: NASA/STScI/ESA. (4) The Tartarus Dorsa mountains on Pluto, view less than 100 miles across. Credit: NASA/JHUAPL/SWRI/New Horizons. (5) The Jovian moon Io - a closeup of one small region on Io's volcanically active surface (over 400 active regions at any given time) taken by the Galileo probe. Credit: NASA / JPL / University of Arizona. (6) Closeup of a cross-section of a meteorite with olivine crystal inclusions (yellow) in a nickel-iron alloy - a centimeter or so across. Credit: J. Debosscher, KU Leuven. (7) A living landscape - the surface of a Purple-striped jellyfish (you can see the original here). Credit: Sanjay Acharya, and Monterey Aquarium/Creative Commons.