Creator has positioned
Jupiter to protect Earth
We live in a cosmic
shooting gallery. In Phil Plait’s Death from the Skies, he lays out
the dangers of a massive impact: destructive shockwaves, tsunamis, flash fires,
atmospheric darkening…. The scenario isn’t pretty should a big one come our
way. Fortunately, we may have a silent guardian: Jupiter.
Is it true that Jupiter could be considered
our friendliest planet because – without Jupiter – comets would be more likely
to hit us?
The answer is yes … Some astronomers
believe that one reason Earth is habitable is that the gravity of Jupiter does
help protect us from some comets. Long-period comets, in particular, enter the
solar system from its outer reaches. Jupiter’s gravity is thought to sling most
of these fast-moving ice balls out of the solar system before they can get
close to Earth. So long-period comets are thought to strike Earth only on very
long timescales of millions or tens of millions of years. Without Jupiter nearby,
long-period comets would collide with our planet much more frequently.
In addition, in recent decades, astronomers
have been able to see signs of comets that have crashed into Jupiter. There was
Comet Shoemaker-Levy 9 in 1994. And, in 2009, astronomers observed a dark gash
in one side of the giant planet, likely caused by a comet.
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