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Researchers use oldest minerals on Earth to study solar system history

The answer to one of the great mysteries of our solar system’s history may lie within a grain no wider than a single strand of human hair.  Scientists have long known that the mineral zircon is very hardy.  “Zircon tends to stick around for a long time,” said Beth Ann Bell, a fifth-year UCLA graduate student who studies these tiny grains.  And she’s not kidding about zircon’s longevity – the samples she studies are 3.8 to 3.9 billion years old.  The Earth itself is 4.5 billion years old.

With their advisor, UCLA Professor Mark Harrison, Bell and her colleagues study individual zircon grains to better understand a critical and highly controversial event in our solar system’s history known as the Late Heavy Bombardment (LHB).  During the LHB, which occurred between 3.8 and 4.1 billion years ago, a very large number of craters formed on the surface of the Moon.  Analysis of the craters and lunar samples have led some scientists to suggest that the objects that crashed into the Moon were numerous and came from far away, possibly beyond the orbit of Jupiter.  “The whole inner solar system should have been impacted and evidence of the LHB should be detectable anywhere, even on Earth“ said Matthew Wielicki, also a fifth-year graduate student.  But scientists are still uncertain if the LHB actually happened at all.  “There is much debate among planetary scientists as to whether the lunar samples from NASA’s Apollo mission are giving us the full picture of what was happening at that time,” said Wielicki.

To better understand the LHB, Wielicki and Bell analyze zircons on Earth in an attempt to determine whether any of the objects that formed the Moon’s craters also impacted our planet.  Like tiny little clocks, zircons can record the timing of an impact event by the heat signatures it leaves behind.  Some recorded features, known as shock features, are diagnostic of an impact and can cause a grain to appear as though it was shattered.  However, such telltale signs do not always develop, and scientists must instead investigate subtler signs, like the ratios of radioactive elements inside the zircon.

To study element ratios within their zircon grains, Bell and Wielicki use a unique device called a Secondary Ion Mass Spectrometer (SIMS), located at UCLA. “With many techniques you must pulverize your sample, essentially destroying it, in order to study it,” said Bell. With the SIMS, samples are left intact and shot with a beam of energized atoms, or ions, and analyzed in tiny patches.  The SIMS can peer into a grain “one atomic layer at a time,” allowing them to study multiple heating events in a single zircon, said Wielicki.

Cosmic impacts aren’t the only events in Earth’s history that could produce heat signatures in zircon grains.  Using the SIMS, Bell and Wielicki hope to be able to distinguish between zircon grains that have been affected by a meteor impact and those that have been heated by “some other event, like mountain building or volcanism, all which were occurring on Earth during the LHB timeframe.”

Because of efficient weathering and erosion processes, there are no impact craters on Earth which date back to the LHB, so Wielicki works to develop the tools necessary to understand impact-heated zircon grains using zircons from more recent impact events.  Bell then tests the validity of those tools on LHB-age zircons whose history is unknown. “The rocks where we find ancient samples are sedimentary, which means they were once older rocks that eroded, and then turned into the sandstone we see today,” said Bell, “we don’t know what types of rock they originally grew in.”

“We are cornering two parts of a three-fold approach to pin down the LHB,” said Wielicki. The third piece of their approach involves studying zircons from other inner solar system objects. “The real excitement comes when we apply our analytical tools to samples from objects like Vesta,” said Wielicki.  Vesta, the target of NASA’s Dawn mission, is a large asteroid located in the inner solar system that has been cold for a very long time.  Wielicki said, “If we see any heating signal in Vesta’s zircons, we know it must be from an impact.”

For Bell and Wielicki, the picture is far from complete. The LHB, which occurred just before the onset of life on Earth, could have ties to the origins of life.  It is unclear, however, if impacts would have acted as “life frustrators,” slowing life’s development, or if they actually delivered the “building blocks” for life, said Wielicki.  “Understanding the timing of the LHB may help answer some of the questions about life on Earth, but first we need a better understanding of the impact history for the inner solar system,” he said.

Watch a video profile of Matt Wielicki here.  Learn more about his research here.

Watch a video profile of Beth Ann Bell here.  Learn more about her research here.

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Researchers use radar to track near-Earth asteroids and predict hazards

Satellite image of the 1,000 foot radio telescope at Arecibo Observatory. Image Credit: GeoEye

Every year, UCLA graduate student Shantanu Naidu makes a pilgrimage to Arecibo Observatory, a uniquely constructed 300-meter radio telescope on the island of Puerto Rico.  His goal: to determine the shape, spin, orbit, and other physical properties of Near Earth Asteroids (NEAs).  These large chunks of rock left over from the formation of the solar system orbit around the Sun while remaining relatively close to Earth.

Observing asteroids with radio waves is a far cry from the traditional picture of nocturnal astronomers and mountaintop telescope domes housing fragile mirrors and lenses.  Since the wavelengths they employ are far outside the visible light spectrum, radar observations can take place as easily during the day as they can at night.  Likewise, the measurements are not affected by weather because the long wavelength radio waves can easily penetrate cloud layers in Earth’s atmosphere.
Naidu bounces radio waves off his targets and examines the reflected signal to reveal the shape of asteroids that would normally appear as “unresolved points of light” through optical telescopes.  Radio telescopes can both resolve and track these elusive objects.  Radar observations taken from Arecibo over the course of a few hours contain hundreds to thousands of pixels with surface resolutions as fine as 7.5 meters.

One of Naidu’s primary goals is to determine a precise orbit for each NEA he studies. At Arecibo, Naidu can pinpoint the position of an asteroid with an uncertainty of only a few tens of meters, a remarkable feat given that the majority of these objects are more than ten million kilometers from Earth.  The precision of an asteroid’s orbit is important because NEAs occasionally come close to Earth as they orbit around the Sun.  Scientists want to be able to identify any asteroid that could be a potential hazard decades or centuries before impact. “NASA wants to catalog the orbits of as many Near Earth Asteroids as possible so we can predict if any asteroid is going to collide with the Earth and take countermeasures,” said Naidu.  Radar measurements of NEAs enable Naidu and his colleagues to derive orbits for the objects far more accurately than any other method. With a single additional observation, the time interval for reliable trajectory predictions can be improved by a factor of 5 to 10, allowing scientists to chart the position of asteroids over the course of hundreds of years rather than decades.

Radar measurements help provide advanced warning for incoming asteroids, but only a tiny fraction of NEAs are currently being studied.  Naidu and his colleagues have observed roughly four hundred of these nearby asteroids, but scientists estimate that 20,000 NEAs with diameters greater than 100 meters exist in the solar system.

When Naidu observes an asteroid for the first time using radar, he hopes to hit the jackpot and see not just one object, but two or three.  What originally appears to be a single asteroid could instead be an asteroid binary, two asteroids that orbit each other like moons orbiting a planet.  “When we observe, we see that one in every six asteroids larger than 200 meters has a moon around it, so we know that binaries form a significant portion of the NEAs,” said Naidu.  “Fifteen years ago, we didn’t even know that binaries existed.”

Fourth-year graduate student Julia Fang works to model the “orbital architecture” of these complex multi-asteroid systems.  She creates computational models to predict how radiation from the Sun or a close encounter with the gravitational field of a planet could change the orbital paths of a multi-asteroid system.  She hopes to recreate the history of these complicated systems in order to understand what processes might be responsible for producing their current orbits.  “Asteroids provide clues about the orbital history of the planets and how they evolved,” said Fang.

Both Naidu and Fang are advised by UCLA Professor Jean-Luc Margot, one of the world’s foremost experts in high-precision radar observations of asteroids.  Additional information about the UCLA radar program is available at: http://radarastronomy.org.

Learn more about Jean-Luc Margot’s research here.

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Researchers analyze extrasolar asteroids using light from distant stars

An artist interpretation of an asteroid being broken apart. Image Credit: NASA/JPL/Caltech

 

When a Sun-like star reaches the end of its lifetime, it blows off its outer layers in a sustained stellar windstorm, leaving behind an Earth-sized, ultra-dense “white dwarf” star.  Astronomers thought they knew what to expect from these celestial leftovers, but were puzzled over a decade ago when they found that a large fraction of observed white dwarfs emit more infrared light than predicted.  Most white dwarf stars are composed of hydrogen and helium, but spectral measurements of some stars revealed puzzling signals from heavier elements such as calcium.

To UCLA Professor Michael Jura, the presence of additional elements indicated that the stellar atmospheres of these white dwarf stars were contaminated from an outside source.  Many scientists hypothesized that the interstellar medium, a cosmic soup of stray particles inhabiting the space between stars, was responsible for this stellar pollution.  Jura thought the answer might instead lie with extrasolar asteroids.  “It was a mystery.  A number of these stars had been known for quite a few years, but nobody knew quite why they were polluted,” he said.  Jura believes that the stellar contamination occurs when an asteroid perturbed out of its normal orbit plummets towards its parent star and is violently ripped to shreds by gravitational forces.  Starlight from the white dwarf is consequently absorbed by the newly created disk of dust and debris left over from the shattered asteroid.  The dusty ring encircling the star re-radiates the starlight as infrared light that is invisible to the human eye but can be measured by specialized telescopes on Earth.

The swirling cloud made from atomized asteroids does more than absorb light; it eventually becomes part of the star itself.  “What is particularly important is that this disk doesn’t just orbit the star, but that it slowly accretes onto the star,” said Jura.  Bits of asteroid falling into the white dwarf star contaminate the stellar atmosphere with heavier elements that wouldn’t ordinarily be present.  “Because we have these dust disks which are broken-up asteroids, we have a tool for measuring the elemental composition of extrasolar asteroids,” he said.

To figure out what these asteroids were made of before they were destroyed, Jura and his graduate student Siyi Xu use data taken from the Hubble and Spitzer space telescopes.  They also observe using the Keck telescopes on the big island of Hawaii a few nights every year.  So far, they have detected 19 different elements heavier than helium in their white dwarf measurements.

“We find the compositions of extrasolar asteroids are quite similar to meteorites in our own solar system. For one particular star, GD 362, the best match is mesosiderite, a type of stony-iron meteorite,” said Xu.  Oddly enough, Xu is able to measure traces of certain elements in meteorites vaporized by distant stars more easily than scientists studying intact meteorites in their labs.  “It is very hard to measure the bulk composition of a meteorite in a lab without destroying it completely,” Xu said.  “Since the asteroid is already broken up for us, we can measure all of the abundances and make a comparison.”

Determining the composition of extrasolar asteroids may help scientists understand how Earth-like exoplanets around stars are formed.  “We picture that when rocky planets form, they build up from nearby chunks of orbiting rock and debris,” Jura said.  “In our own solar system, that process was somewhat inefficient, so we have asteroids left over.”  Our solar system is one of many planetary systems with surplus building blocks left behind from planet formation; scientists estimate that nearly 30% of white dwarf star systems have extrasolar asteroid populations.

Previously, astronomers have only been able to guess the composition of asteroids in other star systems based on what they have learned about asteroids closer to home.  “We think they are probably the original suite of asteroids that formed when the star was forming planets,” Jura said.  “It’s just plain fun to think that you can actually figure out what these other planetary systems are made out of.”

Watch a video profile of Mike Jura here.  Learn more about his research here.

Watch a video profile of Siyi Xu here.

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Prof. Yin investigates the geology of other worlds

A topographic false-color map of Mars including some of the largest volcanoes and the largest canyon in the solar system. Image Credit: NASA/JPL/Caltech/Arizona

Few people can claim that their children learned to walk in the forests of Yosemite National Park.  Professor An Yin, who has spent much of his 26 years at UCLA conducting fieldwork in Tibet, the Himalayas, and California, can.  Having spent his graduate career investigating remote areas of Glacier National Park, Yin’s mountaineering experience equipped him for the challenging Asian fieldwork and tectonic research that earned him the Donath Medal from the Geological Society of America. “It was a frontier in an area that was not explored before, despite it being on Earth,” said Yin. “Knowing almost nothing about this large area, I tried to make a synthesis.”  Nowadays, Yin spends less time in Tibet and the Himalayas, making only two trips a year, usually to drop off graduate students to conduct their own fieldwork.  Instead, he has directed his interest toward the fledgling field of research known as planetary geology.

In 2008, Yin began applying his Earth geology expertise to landscapes he observed on other planets. “Having limited data to create a tectonic story in large areas of Asia gave me the know-how to explore planet-related problems,” Yin said. “The process turns out to be quite similar.” In his early days of Tibetan research Yin used satellite images to estimate locations of faults before going into the field; similarly, he uses satellite images to understand planetary geology from afar.  Images today, however, provide more clues about the geology.  “High-resolution images have revolutionized mapping and geologic interpretation,” said Yin. “We still can’t determine composition, but we can say for certain how much and in what manner a feature is offset from its original position.”

To explain the features he observes on Mars, Yin has developed a theory that invokes a one-plate tectonic system.  Unlike Earth, which has 15 major tectonic plates that move continuously and are responsible for forming mountains and oceans, Mars has only one plate that moves very slowly.  Moving at a pace 1000 times slower than those on Earth, Mars’ tectonic plate produces  plate-boundary features like volcanoes and faults that materialize in a relatively small area and grow very large.  Maps of Mars show that almost all its prominent features are confined to just one-third of the planet.  Among these features are the colossal Tharsis Montes, three volcanoes so large they could fit 32 of Earth’s three-mile-high Andean volcanoes into the volume they occupy.

Although Mars’ features are grander, they share many characteristics with Earth’s terrain.  This observation led Yin to contemplate the underlying processes that create the two planets’ surfaces.  For not only Mars, but for many planetary bodies, the differences in these processes may be the result of their individual “evolutionary paths,” said Yin.

Piecing together the story of how a planet’s geology has changed over time requires Yin to use all the resources at his disposal. “The problem with planetary geology is that you see a static image,” he said, “the history is harder to show.”  One way of revealing the history is by observing it.  In Yin’s laboratory, he and his graduate students design sandbox experiments to reveal how faults, mountains, and valleys develop.  While these experiments are intended to mimic natural conditions, they do not represent the exact history of any process, and act more as a guide to help determine whether their basic assumptions are correct.

From these experiments, Yin has determined that the histories of Mars and Earth are quite similar, differing only in their rates of evolution.  “Mars is smaller and has less heat, so the driving engine is not as powerful as Earth’s,” said Yin.  Although Mars and Earth appear to be quite similar, other planetary bodies may have very dissimilar evolutionary paths.

Yin’s newest foray into planetary science involves Enceladus, an icy moon of Saturn.  He interprets the famous “Tiger Stripes” that periodically eject water vapor from its south pole as a product of the movement of the moon’s icy shell, and prefers to call them “Horsetails,” after a Himalayan feature they so closely mimic.  While Yin can decipher portions of Enceladus’ history from its surface features, it remains unclear whether there is a global or localized ocean beneath the icy surface. “This is an actively debated subject,” said Yin, “but for now I can only tell the story of what happened.”

From the otherworldly geology he’s studied thus far, Yin has learned that “the planetary world is something that defies common sense in many respects.  We have an idea of how a planet should develop and what it should look like, and we find exception after exception after exception.” Yin hopes that his continued interdisciplinary approach to planetary geology will result in observing “overlapping parts of commonality” between planets that could reveal more about planetary evolution as a whole.

Watch a video profile of An Yin here.  Learn more about his research here.

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UCLA scientists work to forecast space weather

The THEMIS spacecraft in orbit around the Earth. Image Credit: SVS/NASA

The Sun is a veritable force in our solar system.  It emits a tremendous amount of heat and energy, called the solar wind, which constantly blows and buffets the planets at a velocity almost two thousand times faster than the average jet plane.  Akin to an invisible shield, the Earth’s magnetic field deflects most of the solar wind, but it happens often that the magnetic fields of the Earth and Sun briefly and directly come into contact with one another.

When the fields connect, part of Earth’s magnetic field “peels away from the sunward side and drapes around the back of the planet,” said sixth-year graduate student, Christine Gabrielse.  The backside of Earth’s magnetic field, or magnetotail, is “squeezed from the outside as a result of the peel back,” she said.  Eventually, two points on the interior of the Earth’s magnetic field meet in what is called a near-Earth reconnection, releasing a great deal of energy that flows toward Earth.  “These powerful phenomena, known as substorms, can create more than picturesque auroras”, Gabrielse said. “They can damage spacecraft or astronauts, or even ground-based systems.”  On March 13th, 1989, one such storm caused a legendary power outage in Canada’s Quebec province that left more than three quarters of a million people without power for nearly twelve hours.

While scientists had studied substorms for years, many questions remained regarding these space weather events.  Proposed by UCLA Professor Vassilis Angelopoulos, NASA’s Time History of Events and Macroscale Interactions During Substorms (THEMIS) mission was designed to answer some of these questions.

Launched in February 2007, the mission consisted of five identical satellites deployed to critical locations around Earth.  Unprecedented at the time, THEMIS allowed scientists to track the flow of energy around Earth and determine how and where substorms initiate.  “The spacecraft gave us five pinholes in the magnetic curtain we are trying to see through,” said Drew Turner, an assistant researcher at UCLA working on the THEMIS mission.

From their unique orbits, engineered to simultaneously provide five key perspectives of the vast space environment, the spacecraft quickly solved the questions they’d set out to answer. “In 2008, THEMIS repeatedly showed that reconnection happens in the magnetotail first, activating a substorm,” said Gabrielse.  With its primary goal accomplished, THEMIS set new objectives.  Splitting the satellites into two groups, three continued to orbit Earth, while two were sent to the Moon as a ‘new’ mission called Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS).  “The extension to ARTEMIS was quite miraculous,” said Turner.  “The spacecraft were not equipped with the ability to maneuver out of their orbit.  The THEMIS engineers and operators sent satellites to the Moon by way of tiny puffs of rocket fuel.”

Using “the most comprehensive plasma instruments we’ve sent to the Moon,” the two ARTEMIS satellites are now busy determining the rock types on its surface, said Turner.  The satellites detect small variations in the Moon’s particle and electric fields allowing them to distinguish between different materials.  “It’s a natural way of detecting surface composition from afar,” said Turner.  In addition, the satellites are improving substorm research by studying the Earth’s space environment from their entirely new viewpoint near the Moon.  “With the two spacecraft at the Moon we can test what’s happening on the other side of the reconnection,” said Shanshan Li, a fifth-year UCLA graduate student.  “We can start to form a three-dimensional substorm model of Earth’s space environment.”

The THEMIS satellites that have remained in orbit around Earth are “scientific goldmines,” according to Turner.  Coordinating observations with the Van Allen Probes, a pair of recently launched NASA satellites, they were able to detect a previously unknown layer of charged particles surrounding Earth.  Turner said, “in a huge and complex system, my bread and butter is combining as many satellites’ data as I can to get as complete a global picture as possible.”

With the Sun approaching a period of increased activity, the media have begun to report space weather more often.  “It’s good to see that society is taking an interest,” said Turner. “We’ve become increasingly dependent on space-based assets,” said Turner. “Even something as simple as using an ATM will most often result in a satellite-relayed signal at some point.” Since large space storms can have huge societal impacts, it is important to be able to see them coming.  “Just like meteorologists want to be able to forecast a storm on Earth, we want to be able to predict a storm in space,” said Gabrielse. “Ultimately, our aim is to determine what’s going on in the Sun-Earth environment and try to better understand it.”

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Prof. Mitchell predicts weather on Titan

Titan in front of Saturn and its rings. Image Credit: NASA/JPL/Caltech/SSI

Saturn’s largest moon, Titan, is an icy world dominated by extensive sand dunes at the equator, methane-filled lakes near the poles, and vast networks of dry riverbeds in between.  Wrapped in a nitrogen atmosphere thicker than Earth’s, Titan is an ideal test bed for studying planetary climate models for UCLA Assistant Professor Jonathan Mitchell.

“Titan is probably the most Earth-like place in the solar system in terms of its very active weather cycle,” said Mitchell. But a weather forecaster on chilly Titan would be more likely to predict a liquid methane downpour than the water-based showers we are accustomed to on Earth.  “Titan is too cold for water to play a role in the weather.  Instead, it rains and hails methane, the natural gas we use as fuel for our stoves,” Mitchell said.

So is Titan a veritable tinder box, an enormous gas leak ready to catch fire at the slightest spark?  Not at all, said Mitchell.  “You might worry about it exploding, but all the oxygen is locked up into water.  If you wanted a lighter that you could carry around on Titan, then you’d carry around a flint with a little vial of oxygen because there is plenty of methane in the air and the limiting ingredient is the oxygen for combustion.”

Titan has surface temperatures nearly 300 degrees Fahrenheit below zero (-180° Celsius).  Water makes up about half the solid body by mass, and where you would expect to find a rocky crust on a terrestrial planet like Earth, Titan’s surface layers are composed mainly of ice.  “Water is essentially Titan’s rock,” said Mitchell.  “These temperatures are so far beyond the realm of human experience that they’re hard to even grasp.”

Despite the frigid conditions, Titan’s climate patterns are technically quite tropical, Mitchell said.  “On Earth, we have a certain temperature difference between the equator and the poles which gives rise to vastly different climates on the surface, like tropical islands versus Antarctica,” he said.  “On Titan, this temperature difference is essentially erased, which makes its climate all tropics.” The subzero weather results from the fact that Titan spins more slowly than Earth, taking sixteen days to complete a full rotation, and also because of its smaller size.  While Titan is larger than Mercury and is the second largest moon in the solar system, it is still less than half the size of Earth.

To be able to understand and predict weather patterns on Titan, Mitchell and his colleagues rely on observations from NASA’s Cassini spacecraft that help them improve their computer simulations.  “We’re looking at the visible and near-infrared images of Titan to survey cloud features and find interesting spatial patterns from the evolution of storms,” Mitchell said.  Because Cassini can only take measurements at Titan during its regular flyby once every few weeks, an accurate computer model is critical to understanding weather patterns on the icy body.

Mitchell’s research may help explain a curious phenomenon called super-rotation, which causes Titan’s atmosphere to circle the planet at speeds higher than expected.  “Super-rotation means that the atmosphere as a whole is spinning faster than the planetary surface,” Mitchell said.  “This is puzzling because we typically think an atmosphere gains its momentum from friction with the surface.”

Since coming to UCLA in 2009, Mitchell has expanded his work to include Earth’s ancient climate, which he hopes will help him to better predict how regional climates will change as the planet warms over the next century.  “We’ve essentially nailed the problem of anthropogenic greenhouse gases warming the planet,” Mitchell said.  “The much harder question is: what will be the resulting impacts?”

Mitchell grew up in rural Iowa where incessant gazing at the stars as a small child led to the occasional tripping injury.  “I’ve always been curious, and that’s what made me a scientist,” Mitchell said.  “I was destined to be looking up.”  As a graduate student at the University of Chicago, Mitchell originally studied cosmology and gravitational lensing.  But after a few years, he switched fields to study the physics of climate on Earth and other planets.  “Cassini was arriving at Saturn about that time so I decided to take a pit stop at Titan, and I haven’t really left since,” he said.

Mitchell, who enjoys singing in small group ensembles in his spare time, has found a home at UCLA.  “Academically, I just can’t imagine a better fit for me.  I have very broad interests and UCLA is a place where you can really expand and learn.”

Watch a video profile of Jonathan Mitchell here.  Learn more about his research here.

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The Gemini Planet Imager will directly image planets around young stars

A simulation of dust rings around a star as they may appear through the Gemini Planet Imager. The morphology of the rings shows an offset from the star, indicating the effects of hidden planets.

Most planet-hunting astronomers infer the existence of extrasolar planets by monitoring tiny changes in the parent stars.  With the recently assembled Gemini Planet Imager (GPI), UCLA Assistant Professor Michael Fitzgerald intends to capture images of these extrasolar planets directly.

Scheduled to go online at the Gemini South Observatory in Chile in late 2013, GPI will be able to detect planets in newly formed systems where traditional detection methods would be likely to fail.  Sensitive at infrared wavelengths, GPI targets young planets, which are warmer than their more evolved counterparts in other systems. “When planets form they are initially large and are slowly contracting, releasing their gravitational energy in the form of heat and cooling off as they get older,” Fitzgerald said.  “We need to look at young systems because that’s when their planets are warmest and therefore brightest in the infrared.”

Using a method based on pioneering work by UCLA Professor Ben Zuckerman, the GPI Exoplanet Survey Team has identified and catalogued over 900 nearby young stars that are promising candidates for planet imaging.  They hope to image 600 of these stars and expect to find roughly fifty new planets.  The type of planets most likely to be revealed by GPI are Jupiter-sized gas giants that formed less than one hundred million years ago and are located many Earth-Sun distances away from their parent star.

But the search won’t be easy.  “Stars are a million times brighter than the planets we are looking for, and these are the biggest and brightest planets that we expect to see,” Fitzgerald said.  The GPI experiment utilizes several state-of-the-art innovations to image these elusive planets including a special coronograph that blocks out light from the parent star in order to make the planet more easily visible, and a unique deformable mirror that helps to compensate for atmospheric distortion.

The best picture astronomers can hope for will show an extrasolar gas giant as a single point of light.  “The planet will not be spatially resolved,” Fitzgerald said.  “We’ll see a dot.”  Yet the GPI instrument can glean a surprising amount of information from a tiny speck of light.  Fitzgerald and his colleagues will be able to analyze the composition of these far-off planets using a spectrograph built by UCLA Professor James Larkin, and perhaps even more importantly, they’ll be able to directly image their associated circumstellar disks.

“A lot of these systems are young – the planets have only recently formed and there are a lot of leftover planetesimals which collide and produce debris disks,” Fitzgerald said.  Scattered light from the dusty cloud surrounding the star has a distinct polarization signature that can be separated from the unpolarized starlight by using special filters.  “If we just look at the intensity of the polarized light, the dust jumps out,” Fitzgerald said.  The shape and position of stellar disks around new stars may help scientists like Fitzgerald better understand the formation of our own solar system.  “There is a lot of diversity in the debris disks we see.  Some of them are rings, some are very extended, a few show interesting asymmetry, and some are even offset from the star due to gravitational perturbations from a planet,” Fitzgerald said.  The structure of dusty disks may also provide clues about the orbital dynamics of distant planets.  “The highlight for the Gemini Planet Imager will be looking at the systems where you have both a disk and a planet, because you can immediately put constraints on the orbit of the planet,” Fitzgerald said.  “If you see a nice, symmetric disk, you wouldn’t expect a planet to be plowing through it.”

Fitzgerald, who came to UCLA in 2010, is also collaborating with scientists at NASA’s Jet Propulsion Laboratory in Pasadena, California to develop a way to make precision radial velocity measurements using infrared rather than visible light.  He hopes the technique will help to find planets around young, energetic stars that are too active to yield accurate results in optical wavelengths, and low mass stars which are optically faint.  Fitzgerald has enjoyed forming new interdisciplinary collaborations in his search for extrasolar planets as a member of iPLEX.  “Having iPLEX and integrating all of the departments in terms of exoplanet studies is definitely the way of the future,” he said.

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UCLA laboratory puts a spin on fluid dynamics

Simulated “Red Spot” on Jupiter created by rotating forced vortices

The Simulated Planetary Interiors Laboratory, known more fondly as the SPINLab, is a state-of-the-art fluid dynamics research facility among only a handful of such unique labs in the world.  Funded by the National Science Foundation, the group is led by Associate Professor Jonathan Aurnou, who has dedicated over ten years of his life to building functional models of planetary cores and atmospheres.

The daily routine for Jon, his graduate students, post-doctoral scholars and researchers involves spinning large, heat-driven containers of water or liquid metal in order to understand the fundamental physics of rotating bodies.  “We are interested in explaining how strongly turbulent systems, like planetary cores and planetary atmospheres, organize into planetary-scale magnetic fields, jet systems, and vortices,” said Aurnou.

The primary device used in the lab, a rotating magnetic convection device (RoMag), is a fluid-filled cylinder that to Aurnou represents “a parcel of fluid inside a planetary core.” “The idea is to study all the ingredients that are involved in planetary core convection and dynamo generation in their simplified state,” said Jonathan Cheng, a fourth-year graduate student with Aurnou.  Dynamos, large-scale magnetic fields generated from the motions of an electrically conducting fluid, are known to exist within planets, stars and even galaxies.  Yet the detailed physics of these natural dynamos remain largely mysterious.

The Earth has a very organized magnetic field, created by convective motions in its rapidly rotating molten metal core, but other bodies such as Uranus and Neptune, the ice giants, and Jupiter and Neptune, the gas giants, have much “messier” dynamos, Aurnou said.  In his lab, however, Aurnou is more concerned with studying the underlying dynamics of fluid systems than reproducing these dynamos.  “I know there are dynamos. There are dynamos all over the solar system and on just about every star,” Aurnou said.  “I’m interested not so much in building a dynamo in my laboratory, but instead in building experiments that allow me to better understand the fundamental physics that underlie dynamo processes.”
And fundamentals have proved successful so far for the SPINLab.  Using RoMag, the team has been able to show drastic differences in rotating convection systems that are metal versus those that are water.  In water experiments, rapidly rotating systems become turbulent much faster than numerical models had predicted.  The interpretation is that planets with deep-water layers can easily break down into turbulent systems that create disordered dynamos, like those we see on the ice giants.

Marie-Curie fellow Michael Le Bars, has been working in the SPINLab for a year, taking part in a long-standing relationship between the lab and French researchers.  Le Bars investigates mixed systems that are partially convecting and partially layered, like those in our atmosphere, oceans, and stars.  These systems were thought to be well understood, but when Le Bars decided to ship his experiments all the way from France to Los Angeles and try rotating them in the SPINLab, the results were surprising.  “Rotation changes everything,” said Le Bars.  One interesting result was the production of “inverse cascades” that create columns of spinning fluid that cut across stratified layers similar to the Great Red Spot on Jupiter.

The fluid dynamics of most turbulent systems studied in the SPINLab are simply too complex for even the most advanced supercomputers to model or predict, but Aurnou and his team realize the importance of combining the two approaches.  They hope to build bridges between experimental and computational methods in order to determine “how to make models that better describe the examples we see in nature.”

Learn more about SPINLab on their website.  Watch the SPINLab educational film project here.

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The Asteroid Vesta in the Light of Dawn

Posted by Michaela Shopland
An image obtained of the asteroid Vesta from NASA’s Dawn spacecraft from a distance of 3,200 miles. Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

On September 27th, 2007, NASA’s Dawn spacecraft left Earth and began a multi-year journey to two of the largest objects in the solar system’s main asteroid belt.  The first stop on its interplanetary roadtrip was the asteroid Vesta.  Dawn reached the Arizona-sized chunk of primordial rock in 2011, providing scientists with the first close-up view of the asteroid’s ancient surface.

A leftover remnant from the formation of the solar system over four billion years ago, Vesta may be similar in composition to the larger bits of celestial debris that originally came together to form the inner planets.  Scientists studying our planet’s origins hope that Vesta will reveal clues about our past that have long been erased by plate tectonics and weathering on Earth.

“Studying Vesta is like going back to the beginning of the solar system,” said Jennifer Scully, a third-year UCLA graduate student working on the Dawn mission. “It is kind of like a fossil of the sort of bodies that were around that combined to make the Earth,” she said.  Scully, the lead mapper for two large areas on Vesta, makes geological maps of the asteroid’s surface in order to interpret the history of different features and formations.

What she has found so far has been surprising.  “We discovered a lot of things that were unexpected at Vesta,” she said.  Grayscale and color images taken by Dawn’s framing camera show a remarkable range of shades on the surface of Vesta, featuring both very bright and very dark material. “It’s very colorful,” said Scully.  “We think the dark material is residue from meteorites called carbonaceous chondrites that have hit the surface.”

Data from Dawn’s instruments including the camera’s seven color filters, a spectrometer, and a neutron detector help scientists characterize surface deposits and divide Vesta into areas depending on age, composition, and morphology.  But sometimes this close-up view of Vesta raises more questions than answers.

“We found both straight and sinuous gully features and I’m investigating what sort of flow(s) formed them,” said Scully. Whether or not some of the gully features could have been carved by molten rock is under investigation.  “The team has not found any definitive features of volcanism,” Scully said.  “There could have been activity early on, but the evidence has been wiped clean by billions of years of impacts.”

Evidence of many of these impacts is preserved on Vesta’s surface in the form of craters. These craters range in size from being so small that Dawn’s camera can barely resolve them to being so large that they have diameters nearly as big as Vesta. The two largest impact basins on the asteroid, named Veneneia and Rheasilvia, are found in Vesta’s southern hemisphere. Scully is one of many Dawn scientists who are working to connect these impact basins with structures in Vesta’s northern hemisphere. “The current understanding is that each of these large impacts sent shock waves through Vesta, which formed large-scale ridges and depressions on the opposite side,” said Scully.

The Dawn spacecraft does not only examine the surface of an asteroid, it can also give scientists clues about its internal structure.  “From the way the gravity pulls on the spacecraft you can tell about the internal layers and the size of the core,” said Scully.  From examining how Vesta’s gravitational field tugs on Dawn, scientists believe that Vesta has a distinct crust, mantle, and core like Earth.

The same is likely not true for the asteroid Ceres, Vesta’s younger cousin and the next and final stop for the Dawn spacecraft.  After remaining in orbit around Vesta for one year, the Dawn spacecraft took its leave in September of 2012 to begin a three-year journey to Texas-sized Ceres, the largest object in the main asteroid belt located between Mars and Jupiter.  Unlike Vesta, scientists think Ceres may harbor large amounts of water ice under its surface.  Because Ceres is wetter than Vesta, it will present a whole new set of questions.  Scully looks forward to directly comparing the data collected from the two asteroids when the spacecraft arrives at Ceres in 2015.

For Scully, the decision to come to UCLA and work with Professor Christopher Russell was a “no brainer.”  “Getting to work on an actual active mission is pretty awesome.  You get to meet a lot of people and really see how a team works,” she said.  In addition to her work on the geology of Vesta, Scully helped create an online system called Asteroid Mappers where citizen scientists can identify features on Vesta using real data collected by Dawn.

Watch a video profile of Jennifer Scully here.  Learn more about her research here.

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UCLA Alum Ashwin Vasavada answers questions about his work with the Mars Science Laboratory

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.