Category: Seminars

While organics and water are among the critical components for life on Earth, carbon containing molecules and water co-exist on many cold bodies in our solar system and on the prestellar (interstellar) ice grains as well. How their journey from these tiny grains in the interstellar medium leads them through the solar system, culminating in comet and asteroid impacts on early Earth – that could have delivered prebiotic materials and triggered evolution of life on Earth – is the focus of Murthy’s research activity at JPL.

 

In this talk, recent research activities at the “Ice Spectroscopy Lab, ISL” at JPL will be discussed. These include new photochemical pathways in Titan’s lower atmosphere [Gudipati, Jacovi et al. 2013], survival depths of organic materials beneath Europa’s surface under electron radiation [Barnett, Lignell et al. 2012], and production of functionalized complex organics in interstellar and cometary ice grains subjected to UV and electron radiation [Gudipati and Yang 2012].

 

 

Acknowledgments:

NASA’s funding through Astrobiology Institute (Titan, a model prebiotic system; Icy Worlds, and Early Habitable Environments), Cassini Data Analysis and Planetary Atmospheres Programs enabled this research, which was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

 

References:

Barnett, I. L., A. Lignell, et al. (2012). “SURVIVAL DEPTH OF ORGANICS IN ICES UNDER LOW-ENERGY ELECTRON RADIATION (<= 2 keV).” Astrophysical Journal 747(1): L24.

Gudipati, M. S., R. Jacovi, et al. (2013). “Photochemical activity of Titan’s low-altitude condensed haze.” Nature Communications 4: 1648.

Gudipati, M. S. and R. Yang (2012). “In-situ Probing of Radiation-induced Processing of Organics in Astrophysical Ice Analogs: Novel Laser Desorption Laser Ionization Time-of-flight Mass Spectroscopic Studies.” The Astrophysical Journal Letters 756(1): L24.

 

Since 1998, under a congressional mandate, NASA has supported several surveys to identify and track Near Earth Objects (NEOs) and the effort continues today to find the smaller potentially hazardous NEOs capable of regional destruction. NEOs are usually found by virtue of their motion against the background stars. All the telescopes currently used for NEO survey were designed for other purposes, and are therefore not optimized for moving objects. We will discuss what makes a survey successful and some of the surprise discoveries by the Catalina Sky Survey.

With Earth-like size and density, Venus should be Earth’s twin. Instead, it lacks plate tectonics and is shrouded by a hot, dense atmosphere with a run away greenhouse. The dramatic divergence of such initially similar terrestrial planets holds lessons for predicting exoplanet behavior. The history of volatiles is clearly central to understanding climate, and also has a major effect on interior evolution. Venus’ atmosphere has lost significant water, yet the interior may have more water than Earth. What are the constraints on water in the interior? Has lithospheric recycling and thus possible volatile recycling occurred? The initiation of subduction is both the gateway to plate tectonics and a key link between interior convection and lithospheric rheology. Numerous potential subduction sites have been identified on Venus. Most of these zones occur in association with corona (possible small-scale mantle upwelling features) and extensional zones. In this talk I will discuss constraints on water in the interior, the evidence for (and against) subduction, and a ‘new’ model for understanding the link between plumes and possible subduction on Venus. This interpretation is based on 1) laboratory fluid dynamics experiments that couple convection and lithospheric deformation and 2) evidence for current volcanism, plumes and possible subduction from gravity, altimetry, radar images and surface emissivity.

The standard core accretion model of planet formation proceeds from condensation through aggregation of dust particles to formation of km-scale, or larger, “planetesimals”. Once planetesimals form, collisional accretion is aided by the gravity of the planetesimals and simulations consistently produce planets from this starting point. The formation of planetesimals has been problematic, however. Formation by gravitational instability is hampered by turbulence in the disk, and formation by collisional accretion has to occur quickly enough to avoid a fiery fate of the proto-planetesimals in the central star due to aerodynamic drag in the disk. I’ll present the results of experiments designed to study the conditions under which accretion may occur. The experiments also have implications for the collisional evolution of planetary ring systems, and for regolith evolution on planetary satellites and asteroids.

Trans-Neptunian Objects (TNOs) are small bodies with orbits beyond Neptune. Roughly 1/3 of TNOs possess peculiarly neutral colors indicative of fresh surfaces, though these objects are thought to be isolated and inactive. To discern between explanations for these neutral colors, we conducted two surveys to search for homogeneity on the surfaces of neutral TNOs – a brightness variation survey in which we sparsely sampled lightcurves of 38 neutral TNOs to select follow-up targets, and a color variation survey of the 9 follow-up targets to densely sample their rotational lightcurves and obtain rotationally phased colors. Our data showcase a surprising number of rotational lightcurves that can only be explained as binaries (some from within the Haumea collisional family). We also found that one of our objects has the fastest measured rotation period of any outer solar system object at 2.4 or 2.6 hours. I will present these results along with updated amplitude and spin distributions for TNOs and comment on what these data suggest about how the dynamical history of the outer solar system.

Understanding kinetic dissipative processes in the solar wind is an important endeavor required to improve our global solar wind models. The candidate dissipative processes must be collisionless in nature and should produce the observed signature of perpendicular anisotropy for protons. Many processes have been proposed e.g. wave-particle interactions, energization at intermittent coherent structures and stochastic heating. We will discuss two efforts related to this line of research:

1) Turbulent Dissipation Challenge: A community driven effort that aims to better quantify the relative contributions of various dissipative processes in the solar wind.

2) Effect of electron equation of state on the kinetics of protons.

Check back later for more details.

We have long known about the great diversity of types of planets found within the solar system.  Thanks to the continuing discovery and characterization of exoplanets, we now know that bulk planetary properties and system architectures also vary significantly between planetary systems.  In this talk, I will discuss some of the possible origins of both intra- and inter-system planetary diversity, and explain how protoplanetary disk observations can be used to directly observe these origins.  In particular, I’ll focus on how spectroscopic observations across a wide range of wavelengths are allowing us for the first time to study the chemical make-up of disks, and to test our understanding of processes such as the condensation sequence and the freeze-out of ices at snow lines.

TBD – please check back later for more details