MessageToEagle.com - It knocked a giant planet into deep space, swallowed up a smaller rival before it could grow any bigger.
Careful observers saw dark spots rapidly changing places and almost a century ago, a luminous protuberance on the eastern
edge of Jupiter, on the equatorial side of the north equatorial belt was reported.
Luminous projections of this kind have often been visible on Mars, but to see them on Jupiter may indicate a real prominence.
Jupiter is a rebel planet with a rich history. We have learned to believe that the presence of a giant, Jupiter-like, planet orbiting
beyond any exo-Earth would be a requirement for life to develop and thrive.
Without Jupiter, the Earth would have been subject to impacts, slowing down or even entirely preventing the development of life on our planet.
We have been taught that collisions with comets and asteroids could endanger all life on Earth; the impact rate of those bodies upon the
Earth would be much higher, were it not for the protective influence of Jupiter.
Is the presence of a giant planet, a necessary condition for life on potentially habitable planets?
Has Jupiter really acted to shield the Earth from impacts since its formation?
Unfortunately, only some research had been done in the past to support this common belief without attempts to investigate whether that is actually the case.
Scientists of Department of Astrophysics and Optics, School of Physics, University of New South Wales, Australia and Astronomy Discipline, Department of Physics,
Astronomy, and Space Science, The Open University, United Kingdom, show that the largest planet in our solar system, is far from being our
true friend. Jupiter-like planets are more likely to put at risk the development of life on otherwise habitable planets and moons.
When it comes to the impact hazard posed by the long-period comets, originating from the Oort cloud, scientists find that Jupiter does offer a significant amount of shielding as a result of the efficiency with which it ejects such comets from the Solar System, never to return.
However, it is generally accepted that these comets represent only a minor contribution (perhaps of order 5%) to the total impact flux at Earth. This result does not, necessarily, infer that the old idea of "Jupiter - the Friend" is justified.
Now, take a look at the potential threats from near-Earth asteroids and short-period comets. The impact rate from them is significantly lower for planetary systems that include a massive Jupiter-like body than for those that have a Saturn-mass (or slightly smaller) planet at the same location.
Does Jupiter protect (or put us in danger) from these objects? Is Jupiter a shield or a threat?
For masses lower than ~0.15 times that of Jupiter, the impact flux experienced by an Earth-like planet falls dramatically in both cases, such that the impact rate were no Jupiter present (or only a very-low mass planet occupied Jupiter's orbit) would actually be lower than that for the scenarios involving our Jupiter.
So, it seems that Jupiter can easily be at least as much, if not more, of a enemy than it is our planet's friend!
Generally, the role of giant planets in influencing the impact flux and the habitability of Earth-like planets is significantly more complicated than was once thought and it is necessary to detect at least some of them to go further in research.
The KEPLER satellite which surveys a large portion of our galaxy to discover terrestrial planets in the habitable zone may contribute with much help.
But which of the many exo-Earths that are found should be prioritised in that search?
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