Astrogeology: September 2011

Jupiter, long settled in its position as the fifth planet from our sun, was a rolling stone in its youth. Over the eons, the giant planet roamed toward the center of the solar system and back out again, at one point moving in about as close as Mars is now. The planet's travels profoundly influenced the solar system, changing the nature of the asteroid belt and making Mars smaller than it should have been. These details are based on a new model of the early solar system developed by NAI scientists at the Virtual Planetary Laboratory, the Goddard Center for Astrobiology, and their colleagues. Their paper appears in a recent issue of Nature.

"We refer to Jupiter's path as the Grand Tack, because the big theme in this work is Jupiter migrating toward the sun and then stopping, turning around, and migrating back outward," says the paper's first author, Kevin Walsh of the Southwest Research Institute in Boulder, Colo. "This change in direction is like the course that a sailboat takes when it tacks around a buoy."

According to the new model, Jupiter formed in a region of space about three-and-a-half times as far from the sun as Earth is (3.5 astronomical units). Because a huge amount of gas still swirled around the sun back then, the giant planet got caught in the currents of flowing gas and started to get pulled toward the sun. Jupiter spiraled slowly inward until it settled at a distance of about 1.5 astronomical units--about where Mars is now. (Mars was not there yet.)

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Source: NAI newsletter

We are pleased to announce the dates for the second workshop on "Titan Through Time: Formation, Evolution and Fate" in 2012, following the very successful first workshop in 2010. The second meeting will have a similar format, with a 2 1/2 science program comprised of themed sessions, and featuring a mixture of invited reviews, and contributed talks and posters.

As in 2010, we welcome scientific reports and attendance from the widest possible cross-section of the scientific community, including both those studying Titan directly, but also those whose research interests have intersections with Titan science in areas such as laboratory chemistry and spectroscopy; modeling of planetary atmospheres, surfaces and interiors; terrestrial analogs and comparative planetology; and the formation and evolution of the solar system.

Further details including the program of invited talks will be publicized in due course. A link to the website (when available) can be booked-marked here:

Hope to see you in 2012.

Conor Nixon, Univerity of Maryland
Ralph Lorenz, Johns Hopkins APL
Co-chairs, science program.

The Lunar and Planetary Institute (LPI), part of the Universities Space Research Association, invites applications for a postdoctoral fellowship in the petrology of planetary materials.

The successful candidate will work with Dr. Allan Treiman in NASA-funded efforts, focusing on planetary crusts and magmas, and their volatiles constituents; target materials include lunar highlands rocks, Martian meteorites, and terrestrial analogs. These efforts focus on planetary samples, starting with analyses by optical microscopy and electron microprobe; other instruments are available at nearby Johnson Space Center or with external collaborators. The candidate will be encouraged to design and conduct their own research in planetary science, propose for external funding, participate in grant review panels and analysis groups, and become involved with spacecraft missions.

The successful candidate will have a recent Ph.D. in petrology or geochemistry; experience with planetary materials is helpful, but not required. The position would be for two years, with possible extension to a third year. Review of candidates will begin on November 15, 2011, with a hiring decision as soon as possible thereafter. Further information can be found on our website: http://

The Universities Space Research Association is an Equal Opportunity Employer.

Some asteroids may have been like "molecular factories" cranking out life's ingredients and shipping them to Earth via meteorite impacts. Now it appears that at least one asteroid may have been less like a rigid assembly line and more like a flexible diner that doesn't mind making changes to the menu.

Astrobiologists at NAI's Goddard Space Flight Center and Carnegie Institution of Washington teams studying the carbon-rich Tagish Lake meteorite have discovered that different pieces of it have greatly differing amounts of amino acids, the building blocks of proteins and essential ingredients to life as we know it.

In January, 2000, a large meteoroid exploded in the atmosphere over northern British Columbia, Canada, and rained fragments across the frozen surface of Tagish Lake. Because many people witnessed the fireball, pieces were collected within days and kept preserved in their frozen state. This ensured that there was very little contamination from terrestrial life.

"The Tagish Lake meteorite fell on a frozen lake in the middle of winter and was collected in a way to make it the best preserved meteorite in the world," said Dr. Christopher Herd of the University of Alberta, Edmonton, Canada, lead author of a paper about the analysis of the meteorite fragments published June 10 in the journal Science.

"The first Tagish Lake samples -- the ones we used in our study that were collected within days of the fall -- are the closest we have to an asteroid sample return mission in terms of cleanliness," adds Dr. Michael Callahan of NASA's Goddard Space Flight Center in Greenbelt, Md., a co-author on the paper.