Strange features of the Solar System – giant gas planets

Steph P. Bianchini February 9, 2017 2 Comments

That our Solar System is an original one, we already know it. Surveys about other planetary systems have confirmed what we already suspected about the odd positions of our gas giants and other features (for a good explanation, read this one). Also, there have been a lot of discussions in the past regarding the role of Jupiter on life on Earth – especially in its function as a shield for Earth from harmful comets and asteroids.

Now, this seems to be changing. A new study from Kevin Grazier, NASA Jet Propulsion Laboratory in Pasadena, simulated the evolution of tens of thousands of particles in the gaps between the jovian planets for up to 100 million years, and offered a different picture. Not only is the “Jupiter as shield” concept not correct – the planet may or may not shield Earth from comet impacts, but perhaps its role in fostering the development of life on Earth was something different, namely, delivering the volatile materials from the outer Solar System needed for life to emerge. If this is true, Jupiter won’t be the only one in this role. Enter Saturn. Here’s the abstract of Grazier’s article, published in the journal Astrobiology:

“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. 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.” 

[KR, Grazier (2017). Jupiter: Cosmic Jekyll and Hyde. – Astrobiology. 2016 Jan;16(1):23-38. doi: 10.1089/ast.2015.1321. Epub 2015 Dec 23. Retrieved 9 February 2017, from https://www.ncbi.nlm.nih.gov/pubmed/26701303]

Space.com had a good article on this topic, which is worth a reading. What remains true, however, is that Jupiter does destroy comets, whatever this means for Earth and the other planets. For something more about the influence of Jupiter, have a look at this one: