July 2018 Newsletter

Wednesday, August 01, 2018 


A Solar System of Its Own

Catching a lot of news coverage this month was DTM Staff Scientist Scott Sheppard’s discovery of a dozen new moons orbiting Jupiter.  Scott’s observing focus was not originally on Jupiter, but on much more distant regions of the Solar System in his quest for more evidence of the existence of a still undiscovered massive planet in the Kuiper belt.  Jupiter just happened to be within view in the portion of the sky on which Scott pointed the telescope.  The tremendous light-gathering capabilities of modern large ground-based telescopes caught the faint light reflected by Jupiter’s moons, one of which is only about a kilometer in diameter, and Scott’s image analysis software detected any object that moved between two exposures. 

The newly discovered moons bring the total of detected moons orbiting Jupiter to 79.  Scott’s new discoveries occur within two of the three main belts of moons orbiting Jupiter.  One group, the prograde group, orbits in the same direction as Jupiter is rotating, while an outer group, the retrograde group, orbits in the opposite direction.  One of the moons in the orbital region of the retrograde group, however, is orbiting in the opposite direction.  Scott named this moon Valetudo.  Given that Valetudo is swimming upstream against the orbital direction of all the other retrograde moons, its future likely includes a head-on collision with one of the counter-orbiting moons.  Such collisions may well be responsible for creating the large number of moons by fragmentation of what was once a much larger object.  The Carnegie press release on Scott’s discovery was covered by the majority of major news organizations around the world and set new records for redistribution on DTM’s social media accounts.  The animation of the orbiting moons created by DTM’s Roberto Molar was viewed 5,600 times on Facebook and over 125,000 times on YouTube.

Diamond Recycling

Over many years of work, DTM Staff Scientist Steve Shirey has been using diamonds and the mineral inclusions they contain as tracers of processes occurring in the deep Earth.  A key result of this work is confirmation that at least some materials now present hundreds of kilometers deep in Earth’s interior were once at Earth’s surface.  In a paper appearing today in Nature, Shirey along with DTM’s Jianhua Wang, GL’s Emma Bullock and Evan Smith of the Gemological Institute of America examined not the inclusion-rich, and hence gemologically worthless diamonds of their usual studies, but the famous Hope diamond, the most famous blue diamond in existence.  Their work showed that the Hope, and similar blue diamonds, likely originated from depths as great as 400-600 kilometers in Earth’s mantle.  The blue color is caused by the presence of trace amounts of the element boron.

Blue boron-bearing diamond, with dark inclusions of a mineral called ferropericlase that were examined as part of this study. This gem weighs 0.03 carats. Photo by Evan M. Smith/© 2018 GIA

Boron is quite abundant in Earth’s crust, but is very rare in its interior. The boron and also the carbon that constitutes the main mass of the diamond, likely were contributed by seawater alteration of ancient oceanic crust before it sank deep into Earth’s interior.  The sinking, or subduction, of altered oceanic crust into Earth’s interior is the main way that water and carbon are removed from Earth’s surface, regulating the volume of the oceans and the composition of the atmosphere in the process.  Once in Earth’s interior, water serves two important roles.  First, it severely reduces rock strength, assisting rocks to flow plastically when subjected to the great pressures and temperatures of Earth’s interior.  Second, water added to the mantle dramatically lowers the melting point of mantle rocks, instigating the volcanism that creates new crust along subduction zones such as those that ring the Pacific Ocean.  This is the cycle of crust production and destruction that marks plate tectonics and helps explain why Earth remains geologically active, and habitable, 4.56 billion years after its formation.

A Presidential Visit

We were pleased to welcome the new Carnegie President, Dr. Eric Isaacs, for a full day campus visit in early July.  The day started with a pleasant shared breakfast with all employees on the BBR campus, where Dr. Isaacs presented his views on the importance of basic research and Carnegie’s special place in that endeavor.  The rest of the day was spent with tours of all of DTM’s laboratories and conversations with all the staff and postdocs.  We look forward to working with Dr. Isaacs in maintaining and extending the excellence of DTM’s research program in Earth and planetary sciences well into the second century of Carnegie Science.

DTM Director Rick Carlson (left) and new Carnegie President Eric Isaacs at the Institution's Broad Branch Road campus, July 11, 2018. Photo by Roberto Molar Candanosa, DTM.

Early Career Excellence

I am excited to report that a former DTM Postdoctoral Fellow, Aki Takigawa, now a professor at Kyoto University, was just announced as this year’s recipient of the Nier Prize of The Meteoritical Society.  The Nier prize recognizes outstanding research in meteoritics and closely allied fields by young scientists.  While at DTM, Aki investigated the characteristics of presolar grains, particularly corundum or aluminum-oxide, providing information on their history from the time of their formation in the outflow of some distant star to their incorporation within the meteorite that was eventually delivered to Earth and dissected for Aki’s analysis.  Aki is the latest of many DTM winners of this award starting with present staff scientist Larry Nittler, who won the award in 2001, followed by DTM postdocs Steve Desch (2003) and Fred Ciesla (2011).

Aki Takigawa, former DTM Postdoctoral Fellow. Photo courtesy Jan Dunlap, DTM.

Our connection with this award, however, goes much deeper.  The award is named for Alfred O.C. Nier, the father of modern isotope ratio mass spectrometry.  Dr. Nier was the PhD advisor of former DTM Staff Scientist Thomas Aldrich who together pioneered the field of potassium-argon geochronology.  Dr. Nier also served as a member of the 1983 Visiting Committee for our department.  During that visit, Dr. Nier recognized that he and I shared an affection for mass spectrometers, so he pulled me aside, reached into the brief case he was carrying, and with one hand pulled out a working copy of the mass spectrometer he had designed and flown on the Viking mission to Mars followed by a long discussion on how it worked.  We are thrilled to be able to continue Dr. Nier’s legacy by providing the opportunity for highly skilled early career scientists like Dr. Takigawa to pursue their research that illuminates our understanding of the earliest history of the Solar System.  Our hearty congratulations go out to Aki for this much deserved recognition of her major contributions to the field.

 
Richard Carlson, Director, DTM
Carnegie Institution for Science
 

July 2018 Newsletter