|Why don't comets hit Earth?|
|Question Date: 2015-10-22|
That is a great question, in Science; comets are
often referred to as NEO’s, or near Earth objects.
Throughout the evolution of the Earth, these
objects actually have been known to hit Earth.
These impacts have been the cause of many mass
extinctions in Earth’s history, meaning that many
species of plants and animals have been wiped out.
If you take a look at the moon for example, you
can see examples of what these impacts look like,
the craters of the moon are formed from asteroid
and comet impacts.
On Earth, the scars from these impacts have
long been wiped away through geological processes
such as weathering of the Earth’s surface, which
has erased much evidence of these collisions.
Currently, there are actually many asteroids and
comets that pass close by the Earth and a group of
scientists at NASA have been tasked with tracking
these objects. Presently there is no threat of
these large objects hitting Earth. They often
hit the sun or Jupiter, for example, instead of
Earth because they both have much larger masses
and greater gravitational pulls that attract large
objects, like comets and asteroids. So, comets
have the potential to hit Earth, but it is very
rare and many scientists believe that another
comet impact on Earth will not occur for many
thousands of years.
Collisions of asteroids and especially comets
are very, very rare. This is because the
trajectories need to be finely tuned. Impact is in
general a rare event. Hit would be like throwing a
basketball towards a basketball hoop from 30 yards
away. Even a professional basketball player cannot
do that too often...even if she tries 1000 times!
So, although impacts are rare they DO OCCUR
because in geologic time of 4,500,000,000
years, even an event that is RARE will occur.
The last big impact was 65,000,000 years ago
when an asteroid about 6 miles in diameter
collided with Earth at what is now the Yucatan
They do, and it's devastating when it
happens - even a small comet would cause an
explosion like that of a very large nuclear bomb,
and big comets are much, much worse. Fortunately,
it doesn't happen very often.
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