EUROPEAN PLANETARY SCIENCE CONGRESS 2009

EMBARGOED UNTIL 00:01 GMT ON MONDAY 14 SEPTEMBER

Craters on Vesta and Ceres could hold key to Jupiter's age 

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CRATERS ON VESTA AND CERES COULD HOLD KEY TO JUPITER’S AGE

Crater patterns on Vesta and Ceres could help pinpoint when Jupiter began to form during the evolution of the early Solar System.  A study modelling the cratering history of the largest two objects in the asteroid belt, which are believed to be among the oldest in the Solar System, indicates that the type and distribution of craters would show marked changes at different stages of Jupiter’s development.   Results will be presented by Dr Diego Turrini at the European Planetary Science Congress in Potsdam, Germany, on Monday 14 September.

The study, carried out by scientists at the Italian National Institute for Astrophysics in Rome, explored the hypothesis that one or both objects formed during Jupiter’s formation by modelling their cratering histories during the birth of the giant planet.  Their simulation described Jupiter’s formation in three stages: an initial accretion of its core followed by a stage of rapid gas accretion. This is, in turn, followed by a phase where the gas accretion slows down while the giant planet reaches its final mass. During the last two phases Jupiter’s gravitational pull starts to affect more and more distant objects. For each of these phases, the team simulated how Jupiter affected the orbits of asteroids and comets from the inner and outer Solar System, and the likelihood of them being moved onto a collision path with Vesta or Ceres. 

“We found that the stage of Jupiter’s development made a big difference on the speed of impacts and the origin of potential impactors. When Jupiter’s core approaches its critical mass, it causes a sharp increase in low-velocity impacts from small, rocky bodies orbiting nearby to Vesta and Ceres which lead to intense and uniform crater distribution patterns. These low-speed collisions may have helped Vesta and Ceres gather mass.  Once Jupiter’s core has formed and the planet starts to rapidly accrete gas, it deflects more distant objects onto a collision course with Ceres and Vesta and the impacts become more energetic.  Although rocky objects from the inner  Solar System are the dominant impactors at this stage, the higher energies of collisions with icy bodies  from the outer  Solar System make the biggest mark,” said Dr Turrini.

The third stage of Jupiter’s formation is complicated by a period known as the Late Heavy Bombardment, which occurred around 3.8 – 4.1 billion years ago. During this time a significant number of objects, rich in organic compounds, from the outer Solar System were injected on planet-crossing orbits with the giant planets and may have reached the Asteroid Belt.  In addition, Jupiter is thought to have migrated in its orbit around this time, which would have caused an addition flux of impactors on Vesta and Ceres.

The team will have an opportunity to confirm their results when NASA’s Dawn space mission reaches Vesta in 2011 and then flies on for a further rendezvous with Ceres in 2015. Dawn will gather information on the structure and the surface morphology of the two asteroids and send back high-resolution images of crater patterns.

“If we can see evidence of an underlying intense, uniform crater pattern, it will support the theory that one or both of these minor planets formed during the final phases of Jupiter accretion, provided that they aren’t obliterated by the later heavy bombardment.  Dawn will also measure concentrations of organic material, which may give us further information about the collisional history with organic-rich objects from the outer Solar System,” said Dr Turrini.

IMAGES

Artist's concept of the Dawn spacecraft with Ceres and Vesta can be found at:
http://photojournal.jpl.nasa.gov/catalog/PIA12033

FURTHER INFORMATION

The project is a joint effort of the Institute for Physics of Interplanetary Space (IFSI) and the Institute for Space Astrophysics and Cosmic Physics (IASF) in Rome. Both institutes are part of the Italian National Institute for Astrophysics (INAF). The project staff is represented by Dr. Angioletta Coradini from IFSI (project leader and senior researcher at IFSI), Dr. Gianfranco Magni (senior researcher at IASF), Dr. Diego Turrini (post-doc at IFSI) and Dr. Sergio Fonte (PhD student at IFSI).

European Planetary Science Congress (EPSC) 2009

EPSC 2009 is organised by Europlanet, a Research Infrastructure funded under the European Commission’s Framework 7 Programme, in association with the European Geosciences Union. It is the major meeting in Europe for planetary scientists. The programme comprises 37 sessions and workshops covering a wide range of planetary topics.

EPSC 2009 is taking place at the Kongresshotel am Templiner See, Potsdam, Germany from Sunday 13 September to Friday 18 September 2009.
For further details, see the meeting website:
http://meetings.copernicus.org/epsc2009/

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CONTACTS

Dr Diego Turrini
INAF - IFSI
Istituto di Fisica dello Spazio Interplanetario
Area Ricerca Tor Vergata
Via Fosso del Cavaliere, 100
I - 00133 Roma
Italy
Tel.: +39 06 4993 4414
Fax: +39 06 4993 4383
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