The Catholic University of America

Planetary Sciences

Lunar Science

The LRO spacecraft will orbit the Moon for one year beginning in February 2009. LEND, which is part of the LRO science payload will detect hydrogen on the surface of the Moon with spatial resolution of ~10 km, to depths of ~1 meter. R. Starr is a Co-I on LEND which is a Russian provided instrument. Even a fraction of hydrogen as small as 100 ppm will produce a measurable change in the neutron albedo from the surface. In 1998, the Lunar Prospector identified increases in hydrogen abundance in permanently shadowed regions of the Moon close to the poles, assumed to be water-ice at or near the surface. LEND will map the hydrogen abundance at the lunar poles with spatial resolution 3-4 times better than accomplished by Lunar Prospector.

P. Chen together with M. Van Steenberg, R. Oliversen and D. Rabin (GSFC) presented a poster paper entitled "Moon Dust Telescopes, Solar Concentrators, and Structures" at the 212th meeting of the AAS held in St. Louis, MO and at the request of the AAS, P. Chen gave a press conference on the topic. NASA also published an official press release (#060408) detailing the research findings. The subject appeared to be of general interest. A number of press interviews and writeups were generated in publications around the world including MIT Technology Review, ABC News in Science, Science@NASA, National Geographic, the Catholic News Network, and many others.

MESSENGER

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a Discovery mission that is designed to fly by and orbit Mercury. It was launched in August 2004, and has executed one Earth flyby, two Venus flybys and most recently, the first of three Mercury flybys before entering Mercury orbit in March 2011. During the one-year orbital phase, a suite of instruments on board MESSENGER will study the exosphere, magnetosphere, surface, and interior of Mercury. The principal investigator is S. Solomon at Carnegie Institution of Washington. R. Starr is a participating scientist with the MESSENGER geochemistry team that will use data from the X-ray, gamma-ray, and neutron spectrometers to determine the surface composition of Mercury. R. Starr is also the instrument scientist for the MESSENGER X-ray spectrometer experiment.

Mars Exploration

V. Krasnopolsky has continued with ground-based spectroscopic observations of Mars using IRTF for mapping of the O2 dayglow, CO, and search for CH4. The O2 dayglow and CO are the best tracers of photochemistry and dynamic polar processes, respectively. The discovery of the variations in CO and other incondensable gases due to condensation and sublimations of CO2 was made two years before the discovery of variations of argon using the Mars Odyssey orbiter. V. Krasnopolsky made a model for seasonal, latitudinal, and diurnal variations of Mars photo-chemistry.

R. Starr is a Co-I on the Mars Odyssey GRS experiment. Mars Odyssey was launched in April 2001 and began mapping the surface of Mars in February 2002. The GRS is an instrument suite consisting of a gamma-ray spectrometer, a neutron spectrometer and a high-energy neutron detector. The GRS produced global maps of H early in the mission, highlighted by identification of large hydrogen-rich components near both poles. The data indicate the presence of a sub-surface layer enriched in hydrogen (water-ice) overlain by a hydrogen-poor layer that decreases in thickness closer to the poles. More recently, maps of Si, Fe, Cl, K, and Th were published in a special issue of the Journal of Geophysical Research. Mars Odyssey is currently in its second extended mission that will end in 2008, however, a third extended mission of an additional two years has been approved.

B. Bonev in team with P. B. James, M. J. Wolff (STScI), P. C. Thomas (Cornell) used the MOC onboard the MGS to study the behavior of morphological features in the residual south polar cap (RSPC) of Mars and the large-scale variability in the RSPC albedo over a period of four Martian years. The changes in the size of the surface features in the RSPC is caused by back-wasting which was first observed between Mars years (MY) 24 and 25. The changes were observed to be similar through MY 27 as observed during MY25 and M26. The results indicate that layers in the RSPC retreat roughly in proportion to their thickness, which Bonev's group argued could be due a difference in porosity between the layers. However, other factors may be involved. The large-scale albedo of the RSPC decreases as the depressions are uncovered by sublimation of seasonal CO2. However, any inter-annual differences in albedo due to the backwasting process are masked by inter-annual differences in the summer dust opacity in the RSPC.

A. Kutepov, A. Feofilov and M. Smith (GSFC) studied the feasibility of retrieving the Martian middle and upper atmospheric temperatures from the broadband MGS/TES infrared bolometer limb radiance measurements. The first retrieved temperature profiles demonstrated a strong wave pattern with the wavelengths of 15-20 km with 10-15 K amplitudes, similar to what was observed during Viking, Spirit, Opportunity and Pathfinder.

Studies of Venus

A. Aiken and CUA graduated student M. Roberts have investigated the behavior of the night side Venus ionosphere as observed by Pioneer Venus orbiter. Venus with its lack of intrinsic magnetic field, slow rotation, and proximity to the Sun presents a unique ionospheric situation. The lack of a magnetic field results in a direct interaction between the solar wind and the planet's atmosphere and ionosphere. The solar wind interaction leads to the transport of ions to the backside of the planet. Ultimately there is acceleration of some ions leading to transport into the tail region of the solar wind planetary interaction zone. Regions of ionospheric depletion result from this acceleration process. These regions of depletion are termed ionospheric holes and have been easily detected using mass spectrometer on the Pioneer Venus. The nightside Venus ionosphere has been well measured using instruments on the Pioneer Venus. Available data cover a full solar sunspot cycle from December 1978 to October 1992.

Recently, V. Krasnopolsky observed Venus with IRTF and detected, for the first time, OCS in Venus clouds, derived an upper limit to H2S, and measured latitudinal variations of CO and HF. V. Krasnopolsky constructed the first chemical kinetic model for the lower atmosphere of Venus.

Cassini-Huygens

R. Carlson has been responsible for the development, testing, and implementation of radiometric calibration algorithms into the CIRS calibration data system. CIRS is a remote-sensing Fourier Transform Spectrometer on the Cassini orbiter that measures thermal radiation over two decades in wavenumber, from 10 to 1400 cm-1 (1 mm to 7 μm, with a spectral resolution from 0.5 to 15.5 cm-1. CIRS observations provide three-dimensional maps of temperature, gas composition, and aerosols/condensates in the atmospheres of Titan and Saturn with good vertical and horizontal resolution, from deep in their tropospheres to high in their mesospheres. CIRS also maps the thermal and compositional properties of the surfaces of Saturn's icy satellites and rings, characterizing their dynamical and spatial structure and constraining theories of their formation and evolution. A critical category of the algorithms, developed by R. Carlsson's group, suppresses several types of spurious electrical noise interference from CIRS interferograms. A de-spiking algorithm for suppressing 0.5 Hz and 8 Hz noise spikes, and algorithms for removing sine wave effects and ripples in individual and average CIRS interferograms have been developed, tested, and implemented into the CIRS data pipeline. R. Carlson developed algorithms for detecting and characterizing velocity variations in CIRS interferograms and for re-sampling all CIRS calibration interferograms to a common reference laser state. Furthermore, R. Carlson has modified and maintained his CIRS interferogram noise detection algorithm to accommodate changes in the data over time. This algorithm rejects interferometer data unsuitable for calibration.

V. Krasnopolsky coupled a photochemical model of Titan's atmosphere and ionosphere that reflects the Cassini results. The modeling is similar to what were made for Mars and Venus.

Earth's Atmosphere

A. Kutepov with collaborators made an non-LTE analysis of the TIMED/SABER limb observations of infrared emissions of the Earth's mesosphere and lower thermosphere. It was demonstrated that accounting for the redistribution of the ν2-quanta among the first excited levels of various CO2 isotopes significantly improves the agreement between temperatures retrieved from the SABER 15 μm CO2 limb radiances and those obtained in the rocket "falling spheres" experiments as well as with the climatological data. With the revised non-LTE model of the 6.3 μm H2O emissions, they obtained the first reliable SABER water vapor density distributions in Earth's mesosphere and lower thermosphere.

A. Kutepov in collaboration with A. Feofilov, A. Medvedev, P. Hartogh (MPS) and A. Pauldrach (U. Munich) investigated the effect of the small-scale temperature fluctuations associated with gravity waves on the infrared radiative cooling of the Earth's mesopause. They shoved that these fluctuation, which are not captured by modern general circulation models, can cause additional cooling up to 3 K per day.

A. Aiken and CUA graduate student J. Correira investigated the global distribution of atmospheric meteoric material. In its orbit around the Sun, Earth intersects with dust mainly dating back from the formation of the solar system. On average Earth is bombarded by 100 tonnes per day of material, which is observed as meteor showers. These particles are of less than 10-4 g and as a result are ablated and deposited in the upper atmosphere as metal atoms. J. Correira and A. Aikin used the GOME ultraviolet visible spectrometer on the ERS-2 to measure the vertical column densities of meteoric neutral metals and their ions including Mg, Mg+, Fe and Fe+ and reported the seasonal behavior of these metals and ions as a function of latitude. There is a clear summer maximum and a minimum in the winter. The SCIAMACHY instrument on the ERS-3 is capable of both nadir and limb observations and provides an altitude distribution and the total column measurement of the ion and atoms. A suitable algorithm was developed to measure the altitude profile and the column density above and below 120 km by M. Scharringhausen (U. Bremen), A. Aikin, J. Burrows (U. Bremen), and J. Sinhuber (U. Bremen). The column density show little correlation with solar activity.

Cometary Studies

Revealing the compositional diversity of comets has high value for understanding solar system formation, the processing history experienced by organic matter during the transition from interstellar cloud cores to planetary systems, and the possibility for exogenous delivery of water and pre-biotic organics to the early Earth.

V. Krasnopolsky have studied X-rays and solar wind composition in four comets observed with Chandra. Abundances of C, O and Ne in the solar wind were derived from the X-ray spectra.

B. Bonev with collaborators have continued to probe the volatile composition of comets. B. Bonev performed a comprehensive compositional study of comet 8P/Tuttle, analyzing all parent volatiles detected with Keck2/NIRSPEC. He also studied the volatile compositions of comets 73P/Schwassmann-Wachmann 3, C/2000 WM1 (LINEAR), M4/SWAN, C/2001 A2 (LINEAR), and C/2002 T7 (LINEAR). A comprehensive study of comet C/2004 Q2 is undergoing, where the multiple parent volatiles, including HDO and CH3D, are analyzed.

B. Bonev's work on OH "prompt" emission established this approach as a valuable tool for measuring water production in comets and for studying aspects of uni-molecular photo-dissiociation dynamics. B. Bonev and G. Villanueva in collaboration with M.J. Mumma, M. A. DiSanti (GSFC), K. Magee-Sauer (Rowan U.), E. L. Gibb (U. of Missouri), Y. L. Radeva (U. of Maryland/GSFC), H. Böhnhardt, M. Lippi (Max Planck Institute), R. Ellis, G A. Blake, C. Salyk (Caltech), H. Kawakita and H. Kobayashi (Kyoto U.) broke new ground in testing the significance of the ortho-para ratio in cometary water. It has long been suggested that the ortho-para ratio is a cosmogonic invariant that is set when the H2O molecule is formed. If this is the case, then it is a key test of the temperature at which the water in a specific comet is formed and thus of its formation region. B. Bonev measured, for the first time, the ortho-para ratio vs. distance from the nucleus in the coma of an active comet, testing whether it was invariant and reported that this was indeed the case.

S. I. Ipatov obtained a NASA DDAP grant and joined the IACS team in April 2008. Together with M. F. A'Hearn (UMD) he has studied time variations of the relative amounts of particles ejected from the comet Tempel 1 after the Deep Impact collision, and the projections of their velocities onto the plane perpendicular to the line-of-sight. Analysis of the levels of brightness in images made by the Deep Impact cameras during the first 13 minutes after the collision allowed to make conclusons for particles that give the main contribution to the brightness of the cloud of ejected material. The impact could be a trigger of an outburst, and therefore mean velocities of the fast material that mainly contributed to the brightness of the observed dust cloud and the duration of ejection were greater than theoretical estimates. The excess ejection of material to a few directions (rays of ejected material) was more pronounced during the first 100 s.

Methane, an indicator of biology on Earth, was detected on Mars by NASA and CUA scientists (Mumma, Villanueva et al. 2009, Science, (323) 1041). When present, methane occurred in extended plumes released from discrete regions. The principal plume contained ~19,000 metric tons of methane, and the estimated source strength (≥0.6 kilogram per second) was comparable to that of the massive hydrocarbon seep at Coal Oil Point in Santa Barbara, California.