Big Bro Jupiter Saved Earth From destruction
At a certain point in the life of an astronomy fan, there comes a time to answer the question:
Is it true that Jupiter could be considered our friendliest planet because – without
Jupiter – comets would be more likely to hit us?
Well, probably if you ended up on this video it means you are an astronomy fan, and so
you must know how to answer that question.
That's why I made this video.
This video is for you.
Thank me later.
Let's get right to the point.
The answer is yes … and no.
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 – potential destroyers
- 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 time scales of millions
or tens of millions of years.
One may ask: what would happen if there was no Jupiter in the Solar System?
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.
One of the most famous comets that crashed into Jupiter was Comet Shoemaker-Levy 9 hitting
Jupiter in 1994, or the one hitting Jupiter on July 19, 2009, about which NASA said:
"We believe it was a comet or asteroid measuring perhaps a few hundred meters wide.
If something of similar size hit Earth—we're talking about 2000 megatons of energy- there
would be serious regional devastation or a tsunami if it hit the ocean."
But we will talk later in this video about the story of these impacts and how Jupiter
literally saved us.
In order to understand how it can save Earth, it's better to describe a little this colourful
and huge planet.
First, everyone knows that Jupiter is the largest planet in our solar system.
It’s 318 times as massive as Earth and 2.5 times bigger than all the other planets combined.
It's a gas giant, and for a long time scientists haven’t exactly known what lies beyond the
violent swirling clouds in the atmosphere but now we know.
Our solar system began as a disk of dust and gas some 4.6 billion years ago.
The first planets to form with the gas giants - Neptune, Uranus, Saturn and Jupiter - took
shape about the same time as the rest of the solar system, forming around 4.5 billion years
ago.
And we know that Jupiter is mostly made up of hydrogen and helium (about 90 per cent
hydrogen and about 10 helium), almost the same composition as our sun.
Some astronomers call Jupiter a failed star.
However, Jupiter just isn’t massive enough for gravity to trigger nuclear fusion.
The beautiful whirling cloud sand storms that you see in some of the famous Jupiter's images
are about 31 miles thick and are made up of ammonia, ammonium hydrosulfite and water,
which form the distinctive red and white bands.
When you look at Jupiter, you probably think that it must have a solid surface, but he
doesn’t have a true surface.
It's mostly gases and liquids.
And if you sent a spacecraft there, it would have nowhere to land.
But just because the spacecraft wouldn’t have a place to land doesn’t mean it would
fly right through Jupiter’s atmosphere and come out unharmed through the other side.
This is because extreme pressures and temperatures deep inside the planet would crush, melt and
vaporize any spacecraft trying to fly into the planet.
But we still can send – and of course, we have sent - spacecraft to orbit and explore
the planet.
For example, the Juno probe was launched towards Jupiter on august 5th 2011 and arrived in
orbit around the planet on July the 4th 2016, and what we’ve discovered and learned about
Jupiter is incredible: we found that the colourful stripes of swirling gas and dust you see in
Jupiter’s atmosphere were found to run 1800 miles deep and hold so much gas that the mass
is about three times that of the entire Earth.
It was also discovered that Jupiter's atmosphere is rotating differently with zones and bands
rotating at speeds that are different by up to 328 feet per second.
This huge and important planet it's kind of our...big bro!
If Jupiter wasn't that big, its gravity wouldn't have the strength to affect big asteroids'
orbits.
And we would be... bullied from asteroids and comets.
We know this because we saw it with our own eyes.
As we can read on NASA's Website about the impact that occurred in July 2009:
<<It began with a furrowed brow, a moment of puzzlement, quickly dismissed.
The date was July 19, 2009.
Amateur astronomer Anthony Wesley was photographing Jupiter from his backyard observatory in Murrumbateman,
Australia, when something odd caught his eye.
"My attention was fixed on the Great Red Spot, which was setting beautifully over Jupiter's
horizon," recalls Wesley.
"I almost didn't notice the dark blemish near Jupiter's south pole, and when I did, I put
it out of my mind."
It's just another dark storm on Jupiter.
"That's what I thought at first, but something about the dark mark puzzled me, it didn't
look right, and I couldn't stop stealing glances at it."
Slowly, Jupiter's rotation turned the blemish toward Earth, Wesley got a better look at
it, and the truth struck him like a thunderbolt.
It was an impact mark.
Something hit the giant planet!
"We believe it was a comet or asteroid measuring perhaps a few hundred meters wide," says Don
Yeomans of NASA's Near-Earth Object Office at JPL.
"If something of similar size hit Earth—we're talking about 2000 megatons of energy--there
would be serious regional devastation or a tsunami if it hit the ocean."
On July 23rd, the Hubble Space Telescope took its first pictures of the blast site.>>
(show pic: https://science.nasa.gov/files/science-pink/s3fs-public/mnt/medialibrary/2009/08/03/03aug_whathitjupiter_resources/hs-2009-23-a-web_print_strip.jpg)
Another famously observed comet impact that occurred on Jupiter was the one of Comet Shoemaker-Levy
9.
The comet was captured by the gravity of Jupiter, torn apart and then crashed into the giant
planet in July 1994.
But the amazing thing is that when the comet was discovered in 1993, it already had been
torn into more than 20 pieces, travelling around the planet in a two-year orbit.
Further observations revealed the comet was torn apart by tidal forces resulting from
the planet's powerful gravity.
We were able to observe this in the aftermath using the Galileo orbiter and the Hubble space
telescope.
Once again, we watched Jupiter save us from a disgrace.
Thank you, big bro!
By the way, at the beginning of this video, we said that sometimes things could go differently:
it turns out that, sometimes, Jupiter can be dangerous for Earth.
Why?
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Well, as every sibling in the world, Jupiter creates both good and bad conditions for earthly
life.
Consider that its powerful gravity prevented space rocks orbiting near it from coalescing
into a planet, and that’s why our solar system today has an asteroid belt, consisting
of hundreds of thousands of small flying chunks of debris.
Today, Jupiter’s gravity continues to affect the asteroids – only now it nudges some
asteroids toward the sun, where they have the possibility of colliding with Earth.
An interesting story -an interesting example - comes from several centuries ago.
Usually, it’s rare for a comet to come within 1 astronomical unit of Earth (that is, one
Earth-sun distance, 92 million miles, or about 150 million kilometres).
But, in the year 1770, a Comet streaked past Earth at a distance of only a million miles.
(It was still far enough, but it was a very rare event).
After some studies, we realized that the comet had come streaking in from the outer solar
system three years earlier and passed close to Jupiter, which diverted it into a new orbit
and straight toward Earth.
The comet made two passes around the sun and in 1779 again passed very close to Jupiter,
which then threw it back out of the solar system.
It was as if Jupiter aimed at us and missed.
So is Jupiter Earth’s protector?
The answer is...sometimes yes...sometimes no.
Do we have to be afraid of asteroids?
The chances of a civilization-ending collision with a large asteroid or comet-like the six-mile-wide
asteroid that wiped out the dinosaurs 65 million years ago—within our lifetimes or even our
grandchildren’s lifetimes are really very small.
At the other end of the size scale, Earth is bombarded all the time by small asteroids
that burn up or explode harmlessly in the atmosphere.
So it’s not the biggest asteroids or the littlest asteroids we need to worry about:
it’s the ones in between.
Unless we can figure out a way to stop it, someday our planet will be hit by an asteroid
big enough to cause local or regional destruction—or even worldwide climate change from the dust
and gases an asteroid impact can kick up.
It’s not a matter of if, but only a matter of when.
It could happen 500 years from now, or it could happen next Tuesday.
By the way, some scientists are currently studying how to make Earth a safer place day
by day, fighting against the threat of asteroids: there are a lot of people involved in Planetary
Defence.
Most of the techniques that have been proposed to avoid an Earth impact event are linked
to altering the trajectory of an asteroid on a collision course with Earth.
Among these proposals, the one that is currently being considered as more mature, because it
is based on existing and affordable spacecraft technology, is the kinetic impactor, which
changes the orbit of an asteroid by a direct hit of a spacecraft at a very high relative
speed (several km/s).
Researchers from all over the world are currently working on this type of things.
If you are passionate about it, you could become one of them!
Good luck!
"This video ends here!
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