Jupiter and Saturn –“Delivered Components for Life to Form on Earth”

 

 

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Not only is the "Jupiter as shield" concept, implying that the planet shields Earth from comet impacts, not true, but perhaps Jupiter's most important role in fostering the development of life on Earth was just the opposite — delivering the volatile materials from the outer Solar System needed for life to form. This new simulation study, and the previously underestimated role that Saturn may have also played in the evolution of life on Earth.


In "Jupiter: Cosmic Jekyll and Hyde"), Kevin Grazier, PhD, at the NASA Jet Propulsion Laboratory in Pasadena, describes the study in which he simulated the evolution of tens of thousands of particles in the gaps between the jovian planets for up to 100 million years. Based on the results, Dr. Grazier concludes that the widely reported shield role attributed to Jupiter is incorrect.

The simulations showed that Jupiter teams with Saturn to kick a significant fraction of the particles into the inner Solar System and into orbits that cross Earth's path. He proposes that a Solar System with one or more planets similar to Jupiter located beyond the region of potential terrestrial planets is beneficial for the development of life.

"In an unprecedented effort to solve the riddle as to whether jovian bodies shield habitable planets from impacts catastrophic to life, Dr. Grazier presents a modeling study that speaks to the incredible complexity of planetisimal evolution in the Solar System," says Sherry L. Cady, PhD, Editor-in-Chief of Astrobiology and a Chief Scientist at the Pacific Northwest National Laboratory.

"In this paper, we learn that the overly simplistic 'Jupiter as shield' concept is a thing of the past, and future research in this area will require the continued use of the kinds of robust simulation strategies so effectively employed in Dr. Grazier's work."

It has been widely reported that Jupiter has a profound role in shielding the terrestrial planets from comet impacts in the Solar System, and that a jovian planet is a requirement for the evolution of life on Earth. To evaluate whether jovians, in fact, shield habitable planets from impacts (a phenomenon often referred to as the “Jupiter as shield” concept), this study simulated the evolution of 10,000 particles in each of the jovian inter-planet gaps for the cases of full-mass and embryo planets for up to 100 My.

The results of these simulations predict a number of phenomena that not only discount the “Jupiter as shield” concept, they also predict that in a Solar System like ours, large gas giants like Saturn and Jupiter had a different, and potentially even more important, role in the evolution of life on our planet by delivering the volatile-laden material required for the formation of life.

 

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The simulations illustrate that, although all particles occupied “non-life threatening” orbits at their onset of the simulations, a significant fraction of the 30,000 particles evolved into Earth-crossing orbits. A comparison of multiple runs with different planetary configurations revealed that Jupiter was responsible for the vast majority of the encounters that “kicked” outer planet material into the terrestrial planet region, and that Saturn assisted in the process far more than has previously been acknowledged.

Jupiter also tends to “fix” the aphelion of planetesimals at its orbit irrespective of their initial starting zones, which has the effect of slowing their passages through the inner Solar System, and thus potentially improving the odds of accretion of cometary material by terrestrial planets. As expected, the simulations indicate that the full-mass planets perturb many objects into the deep outer Solar System, or eject them entirely; however, planetary embryos also did this with surprising efficiency.

Finally, the simulations predict that Jupiter's capacity to shield or intercept Earth-bound comets originating in the outer Solar System is poor, and that the importance of jovian planets on the formation of life is not that they act as shields, but rather that they deliver life-enabling volatiles to the terrestrial planets.

The research was presented in Astrobiology, a peer-reviewed journal. 

The Daily Galaxy via Mary Ann Liebert

Image credit: lasp.colorado.edu

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