Posted on Mar 5, 2019 in Astronomy, Science
The fact that giant Jupiter-like planets are so rare may be one of the reasons why we have yet to discover intelligent life beyond Earth. In the two years leading up to 1994, astronomers had eagerly watched the progress of a comet called Shoemaker-Levy 9 –the first comet to be observed orbiting a planet –as it journeyed through our solar system before Jupiter’s gravity ripped the comet apart into several fragments up to 1.2 miles in diameter imploding at around 134,000 miles per hour.
The comet itself wasn’t what had attracted astronomers — instead, it was the chance to observe the predicted impact of Shoemaker-Levy 9 with Jupiter. And when Shoemaker-Levy 9 finally did strike Jupiter in July of 1994, in a colossal explosion when the first fragment tore into the planet, creating a nearly 2,000-mile-high fireball with temperatures in excess of 42,000 Fahrenheit.
Jupiter’s Spectacular Shoemaker-Levy 9 Impact –“Came from Previously Unknown Comet Gateway”
Recent studies estimate that the gas giant gets hit 8,000 times more than Earth. But that number might even be higher — we can’t directly observe the far side of Jupiter, after all, and the Shoemaker-Levy 9 collision was one of the first times we thought to even look for celestial bodies impacting Jupiter. It makes sense: Not only is Jupiter a huge target, its mass attracts celestial bodies as they pass through our solar system. How many Shoemaker-Levy type collisions there have been throughout the history of our solar system is anyone’s guess. But it’s a big number, for sure.
“Impact” -The Asteroid That Towered a Mile Above the Cruising Altitude of a 747
Through Earth’s history such collisions occur, on the average every one million year. If this figure is correct, it would mean that intelligent life on Earth has developed only because of the lucky chance that there have been no major collisions in the last 70 million years. Other planets in the galaxy, Hawking believes, on which life has developed, may not have had a long enough collision free period to evolve intelligent beings.
As Stephen Hawking noted, the general consensus is that any comet or asteroid greater than 20 kilometers in diameter that strikes the Earth will result in the complete annihilation of complex life – animals and higher plants.
In early 2019, a NASA glaciologist reported a possible second impact crater buried under more than a mile of ice in northwest Greenland. This follows the finding, announced in November 2018, of a 19-mile-wide crater beneath Hiawatha Glacier – the first meteorite impact crater ever discovered under Earth’s ice sheets. Though the newly found impact sites in northwest Greenland are only 114 miles apart, at present they do not appear to have formed at the same time.
“Day the Earth Changed” –Unveiled by a Young 31-Kilometer-Wide Greenland Crater
If the second crater, which has a width of over 22 miles, is ultimately confirmed as the result of a meteorite impact, it will be the 22nd largest impact crater found on Earth.
“We’ve surveyed the Earth in many different ways, from land, air and space – it’s exciting that discoveries like these are still possible,” said Joe MacGregor, a glaciologist with NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who participated in both findings.
Before the discovery of the Hiawatha impact crater, scientists generally assumed that most evidence of past impacts in Greenland and Antarctica would have been wiped away by unrelenting erosion by the overlying ice.
Only about 1 in 1,000 stars are both similar to the sun and have a Jupiter-like planet with a relatively stable orbit in the outer rings of the solar system. The Copernican principle – the idea that the Earth and the solar system are not unique or special in the universe – suggests the architecture of our planetary system should be common. But it doesn’t seem to be.
While the number of known Kepler Mission exoplanets grew rapidly, the Astrophysical Journal reported in 2016 that ground-based extrasolar planet-hunting observations by the Anglo-Australian Planet Search (AAPS) shows that the number of Jupiter-like planets, in Jupiter-like orbits might not be as common as previously thought. The finding reignited the debate about whether the presence of a Jupiter-like planet is necessary for intelligent life.
The Anglo-Australian Planet Search (AAPS) is a long-term program being carried out on the 3.9-meter Anglo-Australian Telescope (AAT) to search for giant planets around more than 240 nearby Sun-like stars.
The impact of the fragments of Comet Shoemaker Levy 9 with Jupiter was the first time astronomers had advance warning of a planetary collision. Many of the world’s telescopes, including the recently repaired Hubble, turned their gaze onto the giant planet reported Inverse.
“The comet crash was also my first professional experience of observational astronomy,” said Michael Brown, Monash University about the Hubble image of the impact of the fragments of Comet Shoemaker Levy 9 with Jupiter –the first time astronomers had advance warning of a planetary collision. “From a frigid dome on Mount Stromlo, we hoped to see Jupiter’s moons reflect light from comet fragments crashing into the far side of Jupiter. Unfortunately, we saw no flashes of light from Jupiter’s moons.
“However, Hubble got an amazing and unexpected view. The impacts on the far side of Jupiter produced plumes that rose so far above Jupiter’s clouds that they briefly came into view from Earth.
“As Jupiter rotated on its axis, enormous dark scars came into view. Each scar was the result of the impact of a comet fragment, and some of the scars were larger in diameter than our moon. For astronomers around the globe, it was a jaw-dropping sight.”
Through Earth’s history such collisions occur, on the average every one million year. If this figure is correct, it would mean that intelligent life on Earth has developed only because of the lucky chance that there have been no major collisions in the last 70 million years. Other planets in the galaxy, Hawking believes, on which life has developed, may not have had a long enough collision free period to evolve intelligent beings.
“The threat of the Earth being hit by an asteroid is increasingly being accepted as the single greatest natural disaster hazard faced by humanity,” according to Nick Bailey of the University of Southampton’s School of Engineering Sciences team, who has developed a threat identifying program.
How many times in our galaxy alone has life finally evolved to the equivalent of our planets and animals on some far distant planet, only to be utterly destroyed by an impact? Galactic history suggests it might be a common occurrence.
The Daily Galaxy, Jake Burba, via Inverse.com and The Conversation
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