Electron phase-space holes (EHs) are good indicators of nonlinear activities in space plasmas and have attracted many interests in both observational and theoretical work. In a traditional theoretical picture, EHs are understood as purely electrostatic structures. However, THEMIS observed electromagnetic EHs, which cannot be fully described with traditional theory, in the plasma sheet boundary layer.
This work seeks to understand the magnetic signals of the observed electromagnetic EHs. In addition to the interpretations of the observed magnetic signals, a statistical study of the properties of the observed electromagnetic EHs reveals that those electromagnetic EHs feature fast speeds, large sizes, and strong potentials, which intrigues interests in their generation mechanism and influences on the space plasma environment.
The Institute for Planets and Exoplanets will participate in the Downs Sydrome Association of Los Angeles’ (DSALA) annual event, TwentyWonder, a charity event that brings an incredible assortment of artists, scientists, designers, musicians, comedians, actors, athletes, and circus performers to the Derby Doll Factory for one unforgettable night! iPLEX will host an informational hands-on comet and asteroid booth where participants can interact with scientists from NASA and UCLA that study these objects on a daily basis. The event is hosted by the Los Angeles Derby Dolls, Southern California’s premiere all-female, banked track roller derby league, will host TwentyWonder 2013, DSALA’s fourth annual fundraising event, to take place July 13, 2013 at the Doll Factory. For tickets, please visit the official website. NOTE: This event is restricted to ages 21+.
All proceeds from TwentyWonder benefit Down Syndrome Association of Los Angeles (DSALA), an organization providing support services for individuals with Down syndrome and their families through the development and promotion of education, counseling, employment and recreational programs in the greater Los Angeles area.
Sebastiano Padovan, a graduate student in UCLA’s Department of Earth and Space Sciences working with Professor Jean-Luc Margot has been awarded a Chateaubriand Graduate Exchange Fellowship. The award will allow him to spend 9 months at the Institut de Physique du Globe de Paris (IPGP) to continue his investigation of the interior of Mercury. He will start in January and will be hosted by Mark Wieczorek who is the Group Director for Planetary and Space Sciences at IPGP and a member of the GRAIL, InSight, and BepiColombo teams.
As Deputy Project Scientist of NASA’s Mars Science Laboratory, Ashwin Vasavada works with other mission scientists at the Jet Propulsion Laboratory in Pasadena, CA to decide where the Curiosity rover will next travel on Mars. Vasavada, who received a B.S. in Geophysics and Space Physics from UCLA in 1992, describes what it is like to command a rover on Mars and gives advice to aspiring planetary scientists.
What inspired you to study planetary science and Mars in particular?
The late 1970s and early 1980s are sometimes referred to as the Golden Age of planetary exploration. NASA landed its first spacecraft on Mars, and the twin Voyagers began a ‘grand tour’ of the outer solar system. I remember being fascinated as a young kid by the pictures from these missions, especially those taken from the surface of Mars, as if one were standing right there and looking out at eye level. It was amazing to me that there were entire other worlds out there, exotic, but yet familiar, with rocks and soil and sky. Even though I grew up with the space shuttle, I never wanted to be an astronaut. It was these robotic probes that really took my imagination.
What has been the most exciting part of working on the MSL mission?
After ten years working on MSL, I’ve had practically every emotion. There’s a deep satisfaction in working with a group of talented people who are at the top of their game. JPL has the best engineers around, and they give it their all to help us scientists conduct our experiments on other planets. In 2008, we had to make the difficult decision to delay our launch by two years. The complexity of the rover was proving too challenging for our schedule, and Mars only comes around every two years for a launch. That was tough, but fortunately NASA stuck with it. Given all the great media coverage, you might think I would say that the landing was the most exciting. But actually, the moment I will never forget is the launch of Curiosity from Cape Canaveral. Only then, staring at this massive rocket and hearing it thunder to the sky, did I fully grasp that we little humans were hurling a one-ton emissary to another planet. And my family and close friends were there with me, watching along.
What is your favorite image returned by Curiosity so far?
Probably my favorite images are the distant panoramas of Mt. Sharp, the 3-mile-high mountain that is the main scientific target for Curiosity. It’s a gorgeous mountain, with canyons carved into its slopes by wind and water. The foothills form layered buttes, like the badlands in the Dakotas. You can follow ancient stream beds uphill until they wind around some corner between sheer walls. If we’re fortunate, we’ll be there in a year or so, dwarfed by those hills.
The base of Mt. Sharp, the Curiosity rover’s final destination on Mars. Image Credit: NASA/JPL/Caltech/MSSS
What was your best experience at UCLA?
Attending UCLA couldn’t have worked out better for me. Like many students, I wasn’t exactly sure where I was headed when I arrived. I chose UCLA because, of the schools that gave me admission, it alone excelled in both the sciences and the arts. I was seriously contemplating a career in music back then, and UCLA gave me the chance to continue to perform alongside music majors while studying science. Grad school at Caltech was five years locked in a laboratory, so I’m so grateful that at UCLA I had the classic college experience–weeknights studying hard, then playing in the marching band at the Rose Bowl on Saturday!
What advice would you give to aspiring planetary scientists?
Probably my favorite piece of advice is to not let the ‘planetary’ distract from the ‘scientist’. Many young scientists want to immediately join the current, big mission, almost like running away to the circus. And like the circus, it’s exciting, but somewhat career-limiting! My advice would be to find a research topic you love, maybe even in Earth science, since that’s often where the state of the art resides. Dive into it for graduate school and a few postdocs, and let NASA come knocking on your door to ask you to join the next mission, because you’re now the expert. Stay focused on being the best scientist you can be.
In the standard model, Earth accreted via a series of giant impacts and the last giant impact produced the Moon and fully melted the Earth. The Moon and Earth are identical in multiple isotope systems that show significant variations between most meteorite groups and planetary bodies. Thus, the simplest explanation for the isotopic similarity is that the Moon and Earth’s mantle have a common origin. However, the canonical giant impact model predicts that the Moon is primarily composed of material from the impactor, which should have had a different isotopic signature than Earth. In addition, recent data from the deep mantle demonstrate that the early Earth was not completely mixed and preserves chemical heterogeneities established during Earth’s accretion. Previous Moon-formation studies assumed that the angular momentum after the impact was similar to present day, but N-body simulations of the growth of Earth-mass planets typically find higher spin rates at the end of accretion. I will present a new model for the origin of the Earth–Moon system. A giant impact onto a fast-spinning proto-Earth can produce a disk that is massive enough to form the Moon and composed primarily of material from Earth, but the system would have had more angular momentum than today. Subsequently, the excess angular momentum can be lost during tidal evolution of the Moon via an orbital resonance. The impact energy is primarily deposited in the impacted hemisphere, and the mantle of the post-impact Earth is stably stratified, which would inhibit immediate deep convective mixing. Hence, the Moon-forming impact need not destroy pre-existing chemical heterogeneities in the deep mantle of the proto-Earth. Finally, I will discuss implications for the volatile depletion on the Moon and the formation of Earth’s early atmosphere.
The modern wealth of data on extrasolar planets is a boon to theoretical studies of the origin and evolution of planetary systems. However the great diversity of exoplanet systems also poses challenges to the goal of a coherent, unified theory of planet formation. This talk will present dynamical models of the most crucial stages of planet growth. First I will address the origin of the solid building blocks known as planetesimals. Aerodynamic processes, highlighted by the streaming instability, play a crucial role in the emergence of planetesimals within turbulent gas disks. Such models of early planet growth can be tested with exoplanet statistics and, more directly, with studies of the Kuiper Belt. Shifting to later phases, I will address the accretion of giant planet atmospheres onto protoplanetary cores. I will present models that challenge the conventional wisdom that a 10 Earth mass core is needed to trigger runaway gas accretion. In particular lower core masses suffice in the outer regions of the protoplanetary disk. These models are crucial for understanding the HR 8799 multiplanet system and others that will be discovered in current and future imaging surveys. I will conclude by discussing future prospects for theoretical models to improve our understanding of planets near and far.
Despite the many hundreds of known “giant” exoplanets, theoretical models still struggle to form them. Under the core-accretion, gas-capture model of giant planet formation, it is still challenging to explain how the required ~10 Earth mass rocky/icy cores can form within the lifetime of their host gaseous circumstellar disks. In this talk I will present two different new lines of research to address this timescale dilemma. I will explore whether or not a newly identified, extremely fast aerodynamic aided accretion of “pebbles” may present a mechanism to form giant planet cores extremely rapidly. Then I will discuss how volatile loss from ice-rich cores and the subsequent enrichment of the atmosphere can alter the efficiency of core growth and potentially aid the planet formation process.
Nearly 50,000 years ago, an asteroid fragment slammed into Earth approximately forty miles east of what is now Flagstaff, Arizona. Upon impact, the celestial projectile shattered into thousands of pieces and created a mile-wide hole now known as Meteor Crater. A 357-pound chunk of that original asteroid now stands center stage in the new UCLA Meteorite Museum.
The Canyon Diablo meteorite was donated to UCLA by philanthropist William Andrews Clark, Jr. upon his death in 1934, becoming one of the first specimens entered into the UCLA Meteorite Collection. While originating from sporadic donations and purchases, it has been Professor John Wasson and researcher Alan Rubin who have spent decades building the collection to its 1500-specimen count today. Together, they have made the collection one of the most extensive in the world, but only recently have these unique bits of our solar system’s history been on display for visitors to admire. “For many years, we’ve collected beautiful exhibit specimens, but kept them locked in an inaccessible cabinet,” Rubin said. “It’s nice to put them on display for other people to see.”
Those expecting the museum to be filled with rows of indistinguishable black rocks may be surprised to learn that there are many types of meteorites, ranging from metallic to stony and everything in between. More than one exhibit emphasizes chondrites, a type of meteorite that is a subject of “endless fascination,” according to Rubin. “Chondrites are composed of thousands or millions of tiny spherules, called chondrules.” While each chondrule tells a different story, they are still very much a mystery. “It appears that chondrules formed from clumps of dust in the solar nebula, the gas and dust cloud that was here before the planets and asteroids formed, and were zapped in a way that is still unknown,” Wasson said.
Not all the exhibits display rocks of extraterrestrial origin, however. One exhibit showcases a collection of melted tektites and Libyan desert glass that formed as a result of meteor impacts. Another exhibit offers tips on how to correctly identify meteorites. Rubin, a world expert in meteorite identification, receives phone calls nearly every day from meteorite-hunting hopefuls. While real specimens occasionally come across his desk, the vast majority of these objects come from Earth. The exhibit, entitled “Meteorwrongs,” features some of the more interesting Earthly samples Rubin has accumulated over the years.
Wasson and Rubin hope that the museum will help educate the next-generation of meteorite researchers. “The museum will be a wonderful teaching resource,” Wasson said. “Our goal is to make it the world’s best scientifically-oriented meteorite museum.” Open to the public weekdays from 9am – 4pm, the museum is located in Geology 3697. Admission is free. The museum, still incomplete, will have mounted informational tablets in its final configuration.
The UCLA Meteorite Museum is supported by the Department of Earth and Space Sciences and the Institute for Planets and Exoplanets. Those interested in providing financial support to the UCLA Meteorite Collection should visit http://giving.ucla.edu/meteorites/.
Watch a video profile of Alan Rubin here. Watch a video tour of the meteorite museum here.
A fundamental long-standing question regarding Mars history is whether the flat and low-lying northern plains ever hosted an ocean. The best opportunity to solve this problem is provided by stratigraphic observations of sedimentary deposits onlapping the crustal dichotomy. Here we use high-resolution imagery and topography to analyze a branching network of inverted channel and channel lobe deposits in the Aeolis Dorsa region, just north of the dichotomy boundary. Observations of stacked channel bodies, switches in channel direction tied to a single node, and stratal geometries indicate that these landforms represent exhumed distributary channel deposits. Observations of depositional trunk feeder channel bodies, a lack of evidence for past topographic confinement, channel avulsions at similar elevations, and the presence of a strong break in dip slope between topset and foreset beds suggest that this distributary system was most likely a delta, rather than an alluvial fan or submarine fan. The location of this delta within a thick and widespread clastic wedge abutting the crustal dichotomy boundary, unconfined by any observable craters, suggests a standing body of water potentially 105 km2 in extent or greater, and is spatially consistent with hypotheses for a northern ocean.
I will address several questions related to how much life there might be in our Galaxy:
What affects whether potentially Earth-like exoplanets might be good abodes for life?
What kind of (Milankovitch-like) variations in habitability might be expected in exosolar
systems? And what does the origin of life on Earth tell us about the probability of life
elsewhere in the Galaxy? I will also discuss the longterm evolution of binary systems,
including thermal and chemical changes, and orbital evolution. In particular, Jupiter will
eventually become a hot Jupiter, and if it were somewhat closer to the Sun it would
eventually be tidally engulfed by the future-red-giant Sun.
