Planetary Science Division Research Articles

Venus Flagship Mission Concept: A Decadal Survey Study.

More than any other known planet, Venus is essential to our understanding of the evolution and habitability of Earth-size planets throughout the galaxy. We address two critical questions for planetary science: 1) How, if at all, did Venus evolve through a habitable phase? 2) What circumstances affect how volatiles shape habitable worlds? Volatile elements have a strong influence on the evolutionary paths of rocky bodies and are critical to understanding solar system evolution. It is clear that Venus experienced a different volatile element history from the Earth and provides the only accessible example of one end-state of habitable Earth-size planets. Venus will allow us to identify the mechanisms that operate together to produce and maintain habitable worlds like our own. The (VFM) concept architecture relies on five collaborative platforms: an Orbiter, Lander, variable-altitude Aerobot and two Small Satellites (SmallSats) delivered via a single launch on a Falcon 9 heavy expendable. The platforms would use multiple instruments to measure the exosphere, atmosphere and surface at multiple scales with high precision and over time. VFM would provide the first measurements of mineralogy and geochemistry of tessera terrain to examine rocks considered to be among the most likely to have formed in a habitable climate regime. Landed, descent, aerial and orbital platforms would work synergistically to measure the chemical composition of the atmosphere including the Aerobot operating for 60 days in the Venus clouds. Loss mechanisms would be constrained by the SmallSats in two key orbits. The baseline payload for VFM includes instruments to make the first measurements of seismicity and remanent magnetism, the first long-lived (60 day) surface platform and the first life detection instrument at Venus to interrogate what could be an inhabited world. The VFM concept directly addresses each of the three Venus Exploration Analysis Group (VEXAG) goals as well as several of the strategic objectives of the 2020 NASA Science Plan, Planetary Science Division, Heliophysics and Astrophysics. The simultaneous, synergistic measurements of the solid body, surface, atmosphere and space environment provided by the VFM would allow us to target the most accessible Earth-size planet in our galaxy, and gain a profound new understanding of the evolution of our solar system and habitable worlds.

Planetary matters

More than 1,700 planetary scientists from 52 countries gathered in Geneva, Switzerland, in September for the joint meeting of the Europlanet Society’s European Planetary Science Congress and the meeting of the Division for Planetary Sciences of the American Astronomical Society.

NASA’S PLANETARY GEOLOGIC MAPPING PROGRAM: OVERVIEW

Abstract. NASA’s Planetary Science Division supports the geologic mapping of planetary surfaces through a distinct organizational structure and a series of research and analysis (R&A) funding programs. Cartography and geologic mapping issues for NASA’s planetary science programs are overseen by the Mapping and Planetary Spatial Infrastructure Team (MAPSIT), which is an assessment group for cartography similar to the Mars Exploration Program Assessment Group (MEPAG) for Mars exploration. MAPSIT’s Steering Committee includes specialists in geological mapping, who make up the Geologic Mapping Subcommittee (GEMS). I am the GEMS Chair, and with a group of 3-4 community mappers we advise the U.S. Geological Survey Planetary Geologic Mapping Coordinator (Dr. James Skinner) and develop policy and procedures to aid the planetary geologic mapping community. GEMS meets twice a year, at the Annual Lunar and Planetary Science Conference in March, and at the Annual Planetary Mappers’ Meeting in June (attendance is required by all NASA-funded geologic mappers). Funding programs under NASA’s current R&A structure to propose geological mapping projects include Mars Data Analysis (Mars), Lunar Data Analysis (Moon), Discovery Data Analysis (Mercury, Vesta, Ceres), Cassini Data Analysis (Saturn moons), Solar System Workings (Venus or Jupiter moons), and the Planetary Data Archiving, Restoration, and Tools (PDART) program. Current NASA policy requires all funded geologic mapping projects to be done digitally using Geographic Information Systems (GIS) software. In this presentation we will discuss details on how geologic mapping is done consistent with current NASA policy and USGS guidelines.

NASA’S PLANETARY GEOLOGIC MAPPING PROGRAM: OVERVIEW

NASA’s Planetary Science Division supports the geologic mapping of planetary surfaces through a distinct organizational structure and a series of research and analysis (R&A) funding programs. Cartography and geologic mapping issues for NASA’s planetary science programs are overseen by the Mapping and Planetary Spatial Infrastructure Team (MAPSIT), which is an assessment group for cartography similar to the Mars Exploration Program Assessment Group (MEPAG) for Mars exploration. MAPSIT’s Steering Committee includes specialists in geological mapping, who make up the Geologic Mapping Subcommittee (GEMS). I am the GEMS Chair, and with a group of 3-4 community mappers we advise the U.S. Geological Survey Planetary Geologic Mapping Coordinator (Dr. James Skinner) and develop policy and procedures to aid the planetary geologic mapping community. GEMS meets twice a year, at the Annual Lunar and Planetary Science Conference in March, and at the Annual Planetary Mappers’ Meeting in June (attendance is required by all NASA-funded geologic mappers). Funding programs under NASA’s current R&A structure to propose geological mapping projects include Mars Data Analysis (Mars), Lunar Data Analysis (Moon), Discovery Data Analysis (Mercury, Vesta, Ceres), Cassini Data Analysis (Saturn moons), Solar System Workings (Venus or Jupiter moons), and the Planetary Data Archiving, Restoration, and Tools (PDART) program. Current NASA policy requires all funded geologic mapping projects to be done digitally using Geographic Information Systems (GIS) software. In this presentation we will discuss details on how geologic mapping is done consistent with current NASA policy and USGS guidelines.

Solar System Observations with the James Webb Space Telescope

The James Webb Space Telescope (JWST) will enable a wealth of new scientific investigations in the near- and mid-infrared, with sensitivity and spatial/spectral resolution greatly surpassing its predecessors. In this paper, we focus upon Solar System science facilitated by JWST, discussing the most current information available concerning JWST instrument properties and observing techniques relevant to planetary science. We also present numerous example observing scenarios for a wide variety of Solar System targets to illustrate the potential of JWST science to the Solar System community. This paper updates and supersedes the Solar System white paper published by the JWST Project in 2010. It is based both on that paper and on a workshop held at the annual meeting of the Division for Planetary Sciences in Reno, NV, in 2012.

Scientists Decry Cuts That Would Doom ExoMars Missions

The president's 2013 budget request eliminates funding for the 2016 Mars mission called Trace Gas Orbiter, which received $27 million this year, as part of a 20% cut to NASA's planetary science division.

Honors

Among the new members elected to the U.S. National Academy of Sciences in May are five AGU members: Richard Edwards, George and Orpha Gibson Chair of Earth Systems Sciences and Distinguished McKnight University Professor, Department of Geology and Geophysics, University of Minnesota, Minneapolis; T. Mark Harrison, director, Institute of Geophysics and Planetary Physics, and professor of geology, Department of Earth and Space Sciences, University of California, Los Angeles; David Sandwell, professor of geophysics, Institute for Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California, San Diego, La Jolla (president of the AGU Geodesy section); Benjamin Santer, physicist and atmospheric scientist, Program for Climate Model Diagnosis and Intercomparison, Lawrence Livermore National Laboratory, Livermore, Calif.; and Steven Wofsy, Abbott Lawrence Rotch Professor of Atmospheric and Environmental Science, Department of Earth and Planetary Sciences, Harvard University, Cambridge, Mass. Four AGU members are among the 2011 prizewinners announced by the Division for Planetary Sciences (DPS) of the American Astronomical Society on 19 May. The prizes will be presented at the joint meeting of DPS and the European Planetary Science Congress in October. William Ward of the Southwest Research Institute, San Antonio, Tex., is the recipient of the Gerard P. Kuiper Prize for outstanding contributions to the field of planetary science. DPS indicated that Ward originally proposed and evaluated “many dynamical processes that are now cornerstones of current theories of how planets form and evolve” and that his “visionary ideas form the foundation for a significant portion of current work in planetary formation and dynamics.”

Priority Planetary Science Missions Identified

The U.S. National Research Council's (NRC) planetary science decadal survey report, released on 7 March, lays out a grand vision for priority planetary science missions for 2013–2022 within a tightly constrained fiscal environment. The cost‐conscious report, issued by NRC's Committee on the Planetary Science Decadal Survey, identifies high‐priority flagship missions, recommends a number of potential midsized missions, and indicates support for some smaller missions. The report states that the highest‐priority flagship mission for the decade is the Mars Astrobiology Explorer‐Cacher (MAX‐C)—the first of three components of a NASA/European Space Agency Mars sample return campaign—provided that the mission scope can be reduced so that MAX‐C costs no more than $2.5 billion. The currently estimated mission cost of $3.5 billion “would take up a disproportionate near‐term share of the overall budget for NASA's Planetary Science Division,” the report notes.

PRELIMINARY RESULTS FROM NEOWISE: AN ENHANCEMENT TO THEWIDE-FIELD INFRARED SURVEY EXPLORERFOR SOLAR SYSTEM SCIENCE

The Wide-field Infrared Survey Explorer (WISE) has surveyed the entire sky at four infrared wavelengths with greatly improved sensitivity and spatial resolution compared to its predecessors, the Infrared Astronomical Satellite and the Cosmic Background Explorer. NASA's Planetary Science Division has funded an enhancement to the WISE data processing system called "NEOWISE" that allows detection and archiving of moving objects found in the WISE data. NEOWISE has mined the WISE images for a wide array of small bodies in our solar system, including near-Earth objects (NEOs), Main Belt asteroids, comets, Trojans, and Centaurs. By the end of survey operations in 2011 February, NEOWISE identified over 157,000 asteroids, including more than 500 NEOs and ∼120 comets. The NEOWISE data set will enable a panoply of new scientific investigations.

The Kuiper Belt Loses Some of Its Mystery

AAS DIVISION FOR PLANETARY SCIENCESPASADENA, CALIFORNIA-- A recent contender for an all-encompassing scenario that will put each planet, asteroid, and icy leftover of solar system formation in its proper place got another test at the American Astronomical Society Division for Planetary Sciences meeting, held here from 8 to 13 October. ([Read more][1].) [1]: http://www.sciencemag.org/cgi/content/full/314/5799/590a

Martian Methane: Rocky Birth, Then Gone With the Wind?

DIVISION FOR PLANETARY SCIENCES MEETINGCAMBRIDGE, U.K.-- About 850 planetary scientists gathered here from 4 to 9 September at the 37th meeting of the American Astronomical Society's Division for Planetary Sciences. The origins of Mars's methane was one of the topics discussed.

Volcanoes, Monsoons Shape Titan's Surface

DIVISION FOR PLANETARY SCIENCES MEETINGCAMBRIDGE, U.K.-- About 850 planetary scientists gathered here from 4 to 9 September at the 37th meeting of the American Astronomical Society's Division for Planetary Sciences. The rugged surface of Titan, Saturn's largest moon, was among the topics of discussion.

Snapshots From the Meeting

DIVISION FOR PLANETARY SCIENCES MEETINGCAMBRIDGE, U.K.-- About 850 planetary scientists gathered here from 4 to 9 September at the 37th meeting of the American Astronomical Society's Division for Planetary Sciences. Snapshots from the meeting include a recently discovered miniplanet in the outer solar system and a possible mechanism for creating the large number of "irregular" satellites that swing around the giant planets in slow, eccentric, tilted orbits.

Several New Twists for Saturn's Rings

CAMBRIDGE, U.K.-- About 850 planetary scientists gathered here from 4 to 9 September at the 37th meeting of the American Astronomical Society9s Division for Planetary Sciences. Topics included some baffling new discoveries about Saturn9s rings.

Amazing Shrinking Kuiper Belt Objects

DIVISION FOR PLANETARY SCIENCES MEETINGLOUISVILLE, KENTUCKY-- About 700 solar system researchers met here 8 to 12 November at the annual meeting of the Division for Planetary Sciences. It was reported that thanks to two independent means of determining the true reflectivity of subplanetary-size bodies, the so-called Kuiper belt objects now look to be 40% smaller than had been assumed.

Hydrocarbon Seas of Titan Gone Missing

DIVISION FOR PLANETARY SCIENCES MEETINGLOUISVILLE, KENTUCKY-- About 700 solar system researchers met here 8 to 12 November at the annual meeting of the Division for Planetary Sciences. Cassini scientists reported that liquids on Saturn's big moon Titan seem to be confined to scattered lakes or even underground, if they exist at all.

Did Jupiter and Saturn Team Up to Pummel the Inner Solar System?

DIVISION FOR PLANETARY SCIENCES MEETINGLOUISVILLE, KENTUCKY-- About 700 solar system researchers met here 8 to 12 November at the annual meeting of the Division for Planetary Sciences. Planetary dynamicists showed how Jupiter and Saturn could have joined forces to fling debris toward Earth from a reservoir in the outer reaches of the solar system.

Publish-or-Perish Perspectives: Dividing Coauthors, Valuing Referees, Taming Expectations

For measuring a scientific journal’s quality, Mohamed Gad-el-Hak supports the impact factor, which he defines as “the total number of citations made in that year for articles published in the two preceding years divided by the number of citable articles published in those years.” A weakness of this factor is that the period between a paper submission and its publication is typically one year, and the two-year period is actually halved. On the other hand, simply noting the weakness may stimulate editors to shorten the publication period.The major shortcoming of assessing scientific productivity by both the number of publications and the number of citations is that such an assessment is typically made without regard to the number of coauthors. This means that a publication’s weight is proportional to the number of coauthors, which looks absurd. It would be more reasonable to assign 0.5 point to the first author and divide the other 0.5 point among the remaining authors. Another, simpler way to assess an individual is to consider the total number of the person’s publications and citations along with the number in which that person is the first or only author.Gad-el-Hak suggests reducing a person’s list of publications to 5–10 significant papers. In my view, it is first necessary to remove all abstracts, conference talks, proceedings, and other unrefereed publications from the listing. Doing so would shorten many lists by a factor of two or three.The number of citations for a published paper depends strongly on how wide the particular field of science is. I work in planetary science, which includes very different fields like geology, atmospheric science, and magnetospheric studies—fields that rarely overlap. Planetary scientists study approximately 20 main bodies (planets and major satellites), asteroids, comets, and interplanetary medium. A paper on, for example, the Martian atmosphere typically would not cite publications on the atmospheres of other planets.The American Astronomical Society’s division for planetary sciences has about 1200 members. Approximately 80% of their publications are in two journals, Icarus and the Journal of Geophysical Research: Planets. These two journals published a total of 418 papers in 2003; the publication rate for members is rather low, approximately 0.45 paper per person per year. But mean number of authors is four per paper, which increases the rate to approximately 1.8. Evidently, citation indices of people who study, say, nitrogen-methane atmospheres of Titan, Triton, and Pluto are much lower than those who study, say, black holes. Therefore, papers in planetary science do not appear in listings of the most cited astronomy and astrophysics publications.© 2004 American Institute of Physics.

Temporal Behavior of Stratospheric Ammonia Abundance and Temperature Following the SL9 Impacts

Infrared emission lines of stratospheric ammonia (NH 3) were observed following the collisions of the fragments of Comet Shoemaker–Levy 9 with Jupiter in July of 1994 at the impact sites of fragments G and K. Infrared heterodyne spectra near 10.7 μm were obtained by A. Betz et al. (in Abstracts for Special Sessions on Comet Shoemaker-Levy 9, The 26th Meeting of the Division for Planetary Sciences, Washington DC, 31 Oct.–4 Nov. 1994, p. 25) using one of the Infrared Spatial Interferometer telescope systems on Mount Wilson. Lineshapes of up to three different NH 3 emission lines were measured at a resolving power of ∼10 7 at multiple times following the impacts. We present here our radiative transfer analysis of the fully resolved spectral lineshapes of the multiple rovibrational lines. This analysis provides information on temperature structure and NH 3 abundance distributions and their temporal changes up to 18 days after impact. These results are compared to photochemical models to determine the role of photochemistry and other mechanisms in the destruction and dilution of NH 3 in the jovian stratosphere after the SL9 impacts. One day following the G impact, the inferred temperature above 0.001 mbar altitude is 283±13 K, consistent with a recent plume splashback model. Cooling of the upper stratosphere to 204 K by the fourth day and to quiescence after a week is consistent with a simple gray atmosphere radiative flux calculation and mixing with cold jovian air. During the first 4 days after impact, NH 3 was present primarily at altitudes above 1 mbar with a column density of (7.7±1.6)×10 17 cm −2 after 1 day and (3.7±0.8)×10 17 cm −2 after 4 days. (Errors represent precision.) We obtained >2.5 times more NH 3 than can be supplied by nitrogen from a large cometary fragment, suggesting a primarily jovian source for the NH 3. By 18 days postimpact, a return to quiescent upper stratospheric temperature is retrieved for the G region, with an NH 3 column density of 7.3×10 17 cm −2 or more in the lower stratosphere, possibly supplied by NH 3 upwelling across an impact-heated and turbulent tropopause, which may have been masked by initial dust and haze. Above the 1-mbar level, the maximum retrieved column density decreased to 6.5×10 16 cm −2. Comparison to photochemical models indicates that photolysis alone is not sufficient to account for the loss of NH 3 above 1 mbar by that time, even when chemical reformation of NH 3 is ignored. We speculate that the dispersion of plume material at high altitudes (above 1 mbar) is responsible for the change in the spectra observed a few days postimpact. Data on the K impact region provide qualitatively consistent results.

Halley's Origins Mysterious No More?

PLANETARY SCIENCEAdvances in computer power have allowed dynamical astronomers to see the inner part of the Oort cloud for the first time and thereby posit the origin of comet Halley and others with similar orbits. They believe it's the innermost part of the Oort cloud, within a distance from the sun of 20,000 times the sun-Earth distance, or 20,000 astronomical units. If the findings, reported at last month's meeting of the Division for Planetary Sciences in Pasadena, California, hold up, they would nail down the location and layout of the last unknown source of comets.