Spring

On Monday, March 25th, I had the honor to give two briefings on the OSIRIS-REx Asteroid Sample Return Mission to policy makers in Washington DC. OSIRIS-REx will visit asteroid 1999 RQ36, a carbon‐ and water‐rich object that is also one of the most potentially hazardous near‐Earth asteroids. This visit was scheduled in conjunction with the OSIRIS-REx Independent Assessment Review (IAR) on March 26th. The IAR is the last of a mission Preliminary Design Reviews and focuses on the credibility of the management, cost, and schedule plans.

My first stop of the day was at the White House Office of Science and Technology Policy (OSTP), where I was scheduled to give a Brown Bag lunchtime seminar on OSIRIS-REx. Jim Green, Director of NASA’s Planetary Science Division, Ed Beshore, OSIRIS-REx Deputy PI, and Shay Stautz, UA Vice President for Federal Relations joined me. We had a full house and several notable attendees including John Holdren, Director of OSTP, Philip Rubin, Principal Assistant Director for Science, and Tammy Dickinson, Senior Policy Analyst and our host. LPL alum Celinda Marsh (M.S., 2007), who now works at the Office of Management and Budget, was also able to join us. The meeting started out on a high note since I was able to pass around several fragments of the Chelyabinsk chondritic meteorite, which had exploded over Russia just one month prior to this presentation. Jim Green provided a nice overview of near-Earth objects and NASA’s wide-ranging efforts to study these bodies. I followed with a detailed overview of OSIRIS-REx, highlighting the exciting science and feed-forward technologies for the agency. Afterwards, Tammy let me know that everyone at OSTP was still talking about both the mission and the sample of Chelyabinsk that I left behind. It had several visitors that afternoon.

Later that afternoon, Shay and I traveled to Capitol Hill to provide a similar briefing for staff members of the House Science, Space, and Technology Committee. UA worked with both full committee staff director Chris Shank as well as with Arizona Representative David Schweikert to arrange that discussion. Our host for this briefing was J.T. Jezierski, Director of Coalitions and Member Services for the Science, Space, and Technology Committee. Staff representing six Committee Members attended. Again, the samples of Chelyabinsk provided an excellent introduction to the scientific value of studying asteroids and meteorites. This venue provided for a more intimate setting, with Shay and I sitting around a conference table with the staff members. I presented a general overview of asteroid science and discussed the OSIRIS-REx mission. The conversation was dynamic and covered a wide range of topics from Solar System to formation to asteroid impact hazards, and resources of near-Earth space. I also left behind a sample of Chelyabinsk for J.T. to pass on the Chairman Lamar Smith. The Chairman used the asteroid fragment to highlight the Chelyabinsk airburst event and kick-off the Full Committee Hearing - Threats from Space: A Review of Private Sector Efforts to Track and Mitigate Asteroids and Meteors, Part II (see photo). 

Overall, the visits to OSTP and Capitol Hill were very successful. Asteroid research and exploration is emerging as a top priority for the United States. This avenue of research is critical to understanding Solar System origins, assessing the asteroid impact threat, and pursuing resource development in near-Earth space.

Kathryn M. Volk defended her dissertation titled "Dynamical Studies of the Kuiper Belt and the Centaurs" on April 1. Kat is a 2013 recipient of the Gerard P. Kuiper Memorial Award, presented each year to students of the Planetary Sciences who best exemplify, through the high quality of their research and the excellence of their scholastic achievements, the goals and standards established by Gerard P. Kuiper, founder of the Lunar and Planetary Laboratory and the Department of Planetary Sciences. During her time as a graduate student, Kat also earned the Graduate Teaching Excellence Award (Fall 2006) as well as the department award for Service and Outreach (2010). She was a two-time recipient of a College of Science Galileo Scholarship (2009 and 2011). This spring, as recipient of the Kuiper award, Kat was the department's nominee for the College of Science Scholarship award. At the College of Science awards ceremony held on April 8, Kat was named as the college-wide awardee for Scholarship, an honor given to the single most outstanding graduate researcher in the entire College of Science. Professor Renu Malhotra was Kat's dissertation advisor.

Kat will begin a position as a CITA (Canadian Institute for Theoretical Astrophysics) postdoctoral fellow at the University of British Columbia Vancouver in the summer of 2013. 

Congratulations, Kat! 

The OSIRIS-REx mission was highlighted in the Spring 2013 edition of Arizona, the UA alumni magazine, with a suite of six articles featuring Professor Dante Lauretta and some of the UA students (graduate and undergraduate) working on the mission project.

OSIRIS-REx Mission: Are We Stardust?

OSIRIS-REx Students

A Scientist, Runner, and Musician Pulls an Intricate Camera System Together - on Deadline

A Sophomore Writes Code to Track a NASA Robot

An Engineer - and his Dog - Settle In To Make History

Creative Writing Meets Planetary Science

The Camera Man

In celebration of Women's History Month 2013 (Women Inspiring Innovation Through Imagination: Celebrating Women in Science, Technology, Engineering and Mathematics), the OSIRIS-REx team developed some online resources for promoting celebrating women in STEM careers. Several current and former LPL faculty, staff, and students are featured, including Nadine Barlow, Veronica Bray, Kat Crombie, Renu Malhotra, Elisabetta Pierazzo, and Elizabeth Roemer. 

Check out the videos, booklists, PowerPoint shows, and biographies online here.

Sarah Mattson, Senior Staff Technician with the HiRISE project, received an Emily Krauz scholarship from the University of Arizona Staff Advisory Council for the fall 2012 semester. The scholarship award is intended to support UA classified staff in career advancement or continuing education and professional development. Sarah applied the award to enrollment in an optics course (Linear Systems and Fourier Analysis).

Congratulations, Sarah!

The first LPL Women's lunch had an impressive turnout of 36 women, representing alumnae, faculty, staff, and grad students, and many people who are combinations thereof.  We came from the Kuiper, Sonett, and Drake buildings as well as JHUAPL, BYU, and Caltech (thanks to the Titan Working Group Meeting for bringing the out-of-towners).  As a result of the lunch, our email discussion list has grown from less than twenty members to over fifty. Anyone interested in joining the email list can subscribe here.

Additionally:

• The personalized tour of HiRISE science operations for Drake Building people after the LPL Staff Colloquium was a joint effort organized by women who made contact at the event. We intend to continue the tradition across the LPL buildings whenever possible.

• Because there is demonstrated interest in continuing group events, Ingrid Daubar and I submitted a mini-grant proposal to the university's Committee on the Status of Women for funding to support future meetings, networking opportunities, guest speakers, and mentoring, community building and outreach events. The mini-grant proposal was successful, and the "LPL Women" project was awarded funds in support of fostering a sense of community within the women of LPL; fostering a sense of community and inclusion on campus by reaching out to other women in science groups through joint discussions or social events; providing time and space to discuss issues such as those raised by the Strategic Planning Committee; increasing awareness of resources and career options; participating as "LPL Women" at LPL general public and children's outeach events.

• A number of LPL Women are now connected to Steward Observatory's Women in Science Forum and vice-versa, a trend Vanessa Bailey (graduate student in Astronomy) and I are actively promoting.

We welcome new members and ideas for further activities!

The UA Campus played host again this spring to the annual Tucson Festival of Books. This year's event, the fifth annual festival, was held March 9-10, 2013; the event was a huge success despite some wild spring weather at the start.

LPL faculty, staff, and graduate students participated in the festival as part of the UA ScienceCity, located on the UA mall directly in front of the Kuiper Space Sciences building. Highlights of the LPL events included OSIRIS-REx staff and ambassadors describing the mission and talking about meteorites and impact cratering. Also featured was Assistant Professor Tamara Rogers, who presented an informal talk on "Mysteries of the Sun: What We Know and What We're Learning." This opportunity for outreach was greatly facilitated with volunteer staffing from the College of Science community volunteers.

The Tucson Festival of Books is free and open to the public. It has become one of the most anticipated and well attended book fairs in the U.S., attracting approximately 100,00 attendees, 450 authors, and 300 exhibitors.

Whether by telescope or spacecraft, when we look at the surfaces of other planets we do so through remote sensing instruments.  There is a wide variety of such instruments from Synthetic Aperture Radars to visible wavelength cameras and an even wider range of geologic features to examine from sand dunes to lava flows.  On Earth, remote sensing is further complicated by vegetation and features constructed by humans.  However, there is one great advantage to remote sensing data analysis on the Earth – you can actually visit the site to test your conclusions…

On this trip we packed our bags for the Mojave Desert, but not before doing some analysis of remotely sensed data from a variety of instruments on both aircraft and spacecraft.  In this way we aim to test our ability (or the data’s ability) to determine something of the surface properties in advance.  The Mojave is a great area for such an experiment both because it has a wide variety of geology and because it is well covered by many different datasets.

After a lengthy drive, our first stop was the Kelso dunes.  Armed with a shovel (the shovel actually saw a lot of use on this trip), we set out to explain the appearance of the dunes in Synthetic Aperture Radar (SAR) datasets. These data show the dunes are dark in the shorter wavelength bands (such as the 5cm C-band) and brighter in the longer wavelength bands (such as the 25cm L-band and 80cm P-band).  Some digging revealed a possible cause – the upper sand is dry quartz grains (with a low dielectric constant that doesn’t scatter radar waves well); however, about 20-30 centimeters (8-12 inches) below the surface a wet layer was found. The longer wavelength radar waves may be sensing this higher dielectric constant layer and scattering more. It was late in the day, but after racking their brains about what to do next some people managed a moonlit hike to the top of the dunes.

Kelbaker Road runs through the Mojave and is full of interesting sites. Just a few miles from Kelso, we stopped at a rock outcrop that we had identified as ‘interesting’ in some hyperspectral imaging data.  Two spectrally distinct rocks were visible here that turned out to be a limestone and a shale. They in turn were quite distinct from the surrounding alluvium, which turned out to be dominated by coarse quartz grains. We pressed onward to Old Government Road, which led us down to Soda Lake (a playa).  SAR data show the playa surface to behave very differently in C, L and P bands and to have large variations from place to place.  Some more digging revealed that many of these differences were probably due to the depth where the playa sediment transitions from dry to wet.  Additionally, roughness differences between parts of the playa dominated by silt and parts dominated by evaporate deposits contributed to the differing radar brightnesses seen in the data. The Cima volcanic field was next door and we stopped here to look at roughness differences between volcanic flows of different ages and how they manifested themselves in the radar data.  Many of the Cima cinder cones also show spectral differences between their summits and lower flanks in our hyperspectral datasets.  Close inspection from hiking to the top and back (which proved to be more involved than expected) of one cone suggested weathering differences of the cinders led to the spectral differences. Finally at Cima we checked out a lava tube cave.  Recent high-resolution planetary cameras have resulted in the discovery of several such caves on Mars and the Moon.

The next day we drove a loop around the Mojave stopping first at some agricultural fields.  Some enigmatic radar-bright radial bands in these circular fields are probably due to concentric ridges at the L-band wavelength scale that result from the concentric planting of alfalfa grass.  The strongly depolarized radar return here is probably due to the vegetation itself.  Such pathological topography (not to mention the vegetation) is unexpected on other planetary surfaces.  Our second stop of the day was the Pisgah lava flow and cone (or rather what’s left of it as it’s being mined away).  We investigated obvious brightness and depolarization contacts in the radar data of the lava field that correlated with dramatic changes in surface roughness.  We also had the chance to explore Glove cave, another lava tube, and hear about the astrobiological research that happened there and its relevance for other lava tubes around the solar system.

Our final stop for this day was the Amboy lava field and cinder cone.  In visible-band orbital imagery the Amboy cone has a dark streak emanating from it to the southeast. Examination of C-band radar data suggests the streak also scatters more radar energy.  Rick Greenberg joined the trip in his plane and flew to Amboy to help us characterize the streak from the air.  On the ground the margins of the streak are very diffuse, but with the help of Rick and his passengers we were able to locate it.  Unfortunately the weather and delays on the road meant we only had the time to map out its northern edge.  The formation of the streak seems to be related to the rate of delivery of silt-size material. Within the streak, this rate seems slow enough that the dark rocks can rise to the surface forming a dark desert pavement with the brighter silt underneath. Outside the streak, continuing silt delivery seems fast enough to keep these dark rocks buried.  The radar brightness difference may also be related to this. Basalt contains appreciable iron, which the silt does not.  A desert pavement of basaltic pebbles is both rougher and has a higher dielectric constant than areas dominated by silt.

Rick and crew landed safely and camped with us in Amboy that night. The next morning we visited Broadwell lake (another playa), which (in contrast to Soda Lake) is homogeneously dark at all radar wavelengths.  The surface here is smooth packed silt and bone dry as far down as we could dig.  There’s nothing in the surface composition or roughness to scatter radar power in the backward direction towards the receiver.

A trip to the Mojave is always fun from a geological perspective. This time however we also gained a little remote sensing intuition.  Other places in the solar system are less easy to visit, but hopefully we can make more sense of their surfaces now.

Despite our tendency to crisscross the whole southwestern U.S. on these trips, there is an incredibly interesting geologic story sitting on our doorstep here in the Tucson area.  There has been growing interest among the fieldtrip group in understanding more about the processes that have fashioned the local landscape around Tucson and that was finally satisfied this semester.

From a geological point of view, we’re fortunate here in the Southwest to be so close to the edge of North America.  Our geologic story is largely shaped by our proximity to this active plate boundary over the past hundred million years or so.  Prior to that, southern Arizona had a mix of dry periods and marine incursions.  One of these marine periods led to the formation of limestone rocks, which would likely have remained obscure were it not for the fabulous caves that formed within them. We had the chance to visit one of these caves at Kartchner Caverns, discovered less than 40 years ago by Gary Tenen and Randy Tufts (an LPL alum).  Other sedimentary rocks that predate the main volcanic and tectonic stories recorded at Tucson can be seen east of the Tucson Mountains too.  However, most of the geologic story we followed started in the late Cretaceous – just before the disappearance of the dinosaurs.

About seventy million years ago there was an oceanic plate (called the Farallon plate), to our west, that was in the process of disappearing beneath North America.  As younger and younger portions of this oceanic plate were dragged beneath our continent they began to float higher and eventually grate along the underside of North America compressing our continent and building mountains.  A wave of volcanic activity passed eastward through the Tucson area ahead of this and large ash-flow calderas dotted the landscape. We visited the remnants of one of these in the Tucson Mountains.  Here, large quantities of volcanic ash are welded together forming the rocks we see (and can be comfortably examined at Gate’s Pass).  During this period, hydrothermal circulation around the subterranean magma chambers led to the concentration of much of Arizona’s copper and other minerals that we continue to mine today.

Probably the most shocking part of this part of the story is that the Tucson Mountains are no longer sitting above the magma chamber that fed them.  That magma chamber is likely part of the Catalina and Rincon mountains on the other side of town! How then did the surface volcanoes end up so far away from where they started?  As the trailing edge of the Farallon plate disappeared beneath North America its angle of descent steepened and it stopped compressing the continent. The mountain ranges produced earlier began to collapse and the crust to spread outward. This crustal spreading manifested itself on the surface in the Tucson area as nearly horizontal faults. Thus the Tucson mountains were able to slide, nearly horizontally, westward off the top of their (now solidified) magma chamber.  Without the weight of the Tucson Mountains above it, the buried granite could rise up buoyantly above the surface.  The Rincon and Catalina Mountains are these magma chambers. We visited the fault where the surface rocks slid off the buried magma chambers to the south and east of these mountains.  Having the surface volcanoes scrapped off like this has consequences for the granite of the magma chamber too. The heat and pressure generated in the region being sheared metamorphoses the granite into mylonite – a rock with a texture that can tell you details of the direction of the shear.  We saw plenty of examples of mylonite on the Catalina Highway – this metamorphism progressed to different extents in different places and is barely apparent at all behind the steep Catalina forerange.  These uplifted partly-metamorphosed magma chambers, where the original surface rocks have been moved off, are called metamorphic core complexes.  They are known to be widespread now, but were first recognized in this classic Tucson example.

Stretching of the crustal rocks continued in a different form as the Farallon plate peeled away from the underside of North America and volcanic activity returned producing dikes that are visible today in the Tucson Mountains.  Steeper faults now formed and occurred in sets that allowed intervening valley floors to drop downward nearly intact.  The alternating basins and mountain ranges this produced can be seen throughout the southwest. Tucson itself sits in one of these basins and we visited a classic example of one of these basin-and-range faults near Oracle named the Pirate Fault.

With the basin floors dropping, the surrounding mountains shed material that began to fill in these low areas.  This continues to this day and we saw examples of bedrock channels and debris flows that have contributed material to the basin fill.  As the mountains erode backward and shed more debris both alluvial fans and pediment surfaces can form.  Compaction of sediment above buried pediments can also lead to fissures opening up on the surface – a process that we saw has accelerated around Wilcox in recent times as groundwater is mined for agriculture.

Within the infilling basins, lakes alternated with playas as climatic conditions shifted. Eventually the basins became so full of sediment that they began to overflow allowing drainage waters to move from basin to basin.  After the basins were integrated in this way lakes gave way to thoroughgoing rivers. The San Pedro river sediments tell this complete story very well and there are great exposures of them in the Saint David’s Formation near Benson.

Despite all the buildings, agriculture and people around Tucson there’s still a lot of geology to see.  This trip has certainly provided us with an appreciation of the local story and how it fits into the broader forces at work as Earth’s tectonic plates (and perhaps those of some extrasolar planes) jostle past each other over geologic time.

On May 1, NASA announced that the OSIRIS-REx target asteroid 1999 RQ36 was renamed Bennu. The name Bennu was selected from over 8,000 entries submitted to the Name that Asteroid! contest. Bennu was an important avian deity in ancient Egypt and one of the symbols of the god Osiris. Egyptians usually depicted Bennu as a gray heron. The double nature of asteroids delivering life’s molecules and sometimes bringing destruction such as the recent fall in Chelyabinsk, Russia, inspired the mission name, OSIRIS-REx, and now the asteroid’s name. Nine-year old Mike Puzio submitted the winning entry, stating, 
“The winged OSIRIS-REx and its heron-like TAGSAM evoke attributes of Bennu, as does the egg shape of the asteroid itself.”

OSIRIS-REx will launch in 2016, rendezvous with Bennu in 2018, and take a sample in 2019.

More information about how Bennu got its name is available on the OSIRIS-REx site and in the UA News press release.