Seminars for Scientists

With large orbital eccentricity and  tilted spin axis we expect Pluto to have extreme seasons with substantial transport of volatiles between hemispheres.  Pluto’s thin atmosphere transports frozen volatiles from areas of high insolation to areas of low insolation. The N2-rich atmosphere is in equilibrium with the frozen N2 on the surface; as the N2-rich volatiles… Read more »

The Lyman Alpha Mapping Project (LAMP) onboard the Lunar Reconnaissance Orbiter (LRO) has been recording far-UV photons reflected from the lunar surface almost continuously since December 2009.  One photon at a time, LAMP builds up spectra from 575 to 1965 Å with a spectral resolution of 26 Å.  The UV geometric albedo spectrum for a… Read more »

Image degradation due to scattered radiation from residual optical fabrication errors is a serious problem in many optical systems operating at short wavelengths or for some optical fabrication processes. Most currently-available image analysis codes (ZEMAX, ASAP, FRED, etc.) require the scatter behavior (BRDF data) as input in order to calculate the image quality from such… Read more »

We have performed an astronomical observing campaign of asteroid (101955) Bennu in support of the OSIRIS-REx mission. The results provide information about the asteroid’s physical, geological, and dynamical properties. We synthesize these data and the results of dynamical modeling to identify likely source regions for Bennu in the Main Asteroid Belt and constrain the pathway… Read more »

How did the early Earth remain warm despite weak solar luminosity?  The faint young Sun paradox has stubbornly resisted a self-consistent solution since it was first introduced by Sagan and Mullen [1] over four decades ago.  However, recent revisions to expected paleo-ocean temperatures [2, 3] along with new results from three-dimensional climate models [4] may… Read more »

Impact craters have been used for decades for a variety of studies across the solar system, and crater populations have been primarily used to model the ages of planetary surfaces.  While age-modeling has a simple premise (a surface is older if it has more craters, and crater density is calibrated to Apollo and Luna sample… Read more »

Aerosol – cloud – rainfall interactions are complicated yet important since changes in rainfall can adversely impact human societies. Though the NASA “A-train” has provided a remarkable set of coordinated satellite experiments by which these interactions can be studied, the interactions are not easy to quantify since the physics is intricate and the retrievals of… Read more »

In recent years, with Earth-orbiting telescopes such as the International Ultraviolet Explorer and the Hubble Space Telescope, significant advances have been made in the area of ultraviolet observations of solar system objects. More in-depth studies have been made using interplanetary probes such as Galileo and Cassini. While the UV spectral range has traditionally been used… Read more »

Solar variability in all its forms has profound effects on the middle and upper atmosphere of the Earth, and on the near-Earth space environment.  These effects increase with increasing altitude, and become dramatic above about 100 km.  Considerable study has been devoted to solar-driven changes to the charged particle environment in the ionosphere and magnetosphere,… Read more »

For planetary scientists, the Galilean moon Europa is amongst the most interesting bodies in the solar system. Its surface composition is revealing the past and recent geophysical processes both on and below the surface, and a dust mass analyzer onboard a satellite orbiting the moon will allow us to acquire this invaluable knowledge. In particular,… Read more »

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New Horizons will revolutionize our understanding of the Pluto system in 2015, but understanding of Pluto’s provenance has been strongly evolving for years. Pluto has emerged as a surviving oligarch/dwarf planet of the primordial planetesimal disk beyond the initial compact planetary configuration. In terms of formation, Pluto accreted in full within a gas-free environment or… Read more »

Total spectral irradiance is typically modelled by assigning an atmospheric model to each pixel of a full disk image and geometricllay combining the predicted wavelength dependent intensity for each of these models into a disk integrated spectrum. This works reasonably well, as the hydrostatic models that are used in this procedure generally reproduce observed spectra very well. However, for numerical… Read more »

Measurements from the Cassini Plasma Spectrometer (CAPS) have revealed the presence of very heavy ions (up to 10,000 amu/q) in the ionosphere of Titan, the largest moon of Saturn. CAPS has also observed O+ flowing into Titan’s atmosphere, which is deposited in the same region where the heavy ions are observed. This leads to the… Read more »

The density and flow direction of plasmas in magnetospheric tails provide important clues to the tail structure and dynamics.  The study of McAndrews et al. [Plasma in Saturn’s nightside magnetosphere and the implications for global circulation, Plan. Sp. Sci. (2009)] examined the properties of magnetospheric plasma primarily in the pre-dawn equatorial region of Saturn’s middle magnetosphere… Read more »

400 years after Galileo pointed a telescope at celestial objects for the first time, neutral atoms were added to the astronomical toolbox with the Interstellar Boundary Explorer (IBEX), launched October 19, 2008. Since early 2009, two energetic neutral atom (ENA) cameras take global images of the solar system’s interaction with its neighborhood. They have returned… Read more »