Jupiter was a ‘rolling stone‘! Part- 2
Yet, if it’s any consolation, Jupiter’s interior is not hellish in all its aspects. In fact, massive wealth awaits anyone who is not electrocuted in the planet’s metallic hydrogen ocean.
You see, scientists believe lightening in the upper atmosphere, turns methane gas into carbon soot. As the carbon-clumps fall, they harden—becoming first, graphite rain, then a cascade of diamonds!
The Jovian enigma began 4.6 billion years ago, as the solar system was taking shape. The favored formation hypothesis is “disk instability,” in which gas and dust swirling around the young Sun fast-tracked Jupiter to giant-hood.
Here, Grand Tack theorists—drawing on an ancient sailing technique—take up the narrative. They paint a picaresque picture of a roving cosmic rascal, wreaking evolutionary havoc in the early solar system: With fortuitous consequences for Earth and Venus, but near ruination for Mars.
Jupiter’s path is referred to as the “Grand Tack,” Kevin Walsh, lead author of an influential 2011 paper told NASA, because the planet was envisioned, “migrating toward the sun and then stopping, turning around, and migrating back outward… like…a sailboat…when it tacks around a buoy”.
As a backdrop, researchers note that, out of 1,800-plus satellites detected around Milky Way stars, 500 or so are in multiple-planet systems. These are mostly “hot Jupiters” or “Super-Earths” (with up to 10 times our planet’s mass), which often orbit closer to their parent stars than Mercury does to the Sun.
Our solar system, the theory goes, was apparently evolving along similar lines—until Jupiter journeyed inward, to about 1.5 astronomical units (AU) from the Sun. (An “AU,” is 149 million km–the distance between Earth and Sun.)
Walsh, of the Colorado (U.S.A.) based Southwest Research Institute, says 1.5 AU is about where Mars is now. His team theorized that gas pressure, the gravity of neighbouring bodies and the Sun’s tidal influence powered Jupiter’s movement.
The Jovian journey ended there, they believe, due to the formation of Saturn—the second largest of the giants and an early travel companion of Jupiter. Saturn too started to move inward, under the influence of gas currents. With the two linked gravitationally, Saturn halted Jupiter’s sunward drift.
Nevertheless, the banded giant got close enough. Its dominating and disruptive gravitational field either broke up or dispatched the first generation of inner solar system planetesamal (and possibly Super-Earths)—creating a dearth of material for planet formation in the region.
This, researchers contend, accounts for both the absence of Super-Earths—which are so numerous among planetary systems detected around other stars–and the smaller size of the Sun’s four terrestrial satellites.
Mars, in particular, was seriously shafted. The Red Planet is just over half the size of Earth, with only about 11 percent of it mass. Astronomers blame this disparity on the incursion of Jupiter in the area, before the formation of Mars. Jupiter threw away much of the material, that Mars would later need.
Comparatively speaking though, the Red Planet was lucky: At least it was able to see the light of existence. Less fortunate, was a fifth rocky planet that would be orbiting in what is now the main asteroid belt—were it not for Jupiter’s gravitational bedlam.
“Jupiter may have acted like a giant wrecking ball…,” wrote Charles Q. Choi, in Space.com, “roaming in to destroy an early generation of inner planets before retreating to its current orbit”.
Having reshaped the inner solar system, Jupiter and Saturn reversed and spiraled off to their present orbital abode: Two rolling stones, roaming in the true blues-folk tradition.