00:00An asteroid, detached from the Moon, has recently moved closer to Earth.
00:04Does it represent a threat to us?
00:06Kamoho Alewa, also known as 2016 HO3,
00:11is spinning at an impressive speed, gravitating near our planet.
00:15To simplify, let's call it HO3.
00:18Astronomers spotted it on April 27, 2016.
00:21Compared to other asteroids, it is tiny.
00:24However, on Earth, it would be the size of a small building,
00:28about half the size of the London Eye's big wheel.
00:31Discovered in Hawaii, its name can be roughly translated as
00:35a oscillating fragment.
00:37After studying it, scientists have hypothesized
00:40that it could be a moonburst projected into space following an impact.
00:44There is an area of the Moon called the Giordano-Bruno crater,
00:48named after an Italian philosopher of the 16th century
00:51who paid his ideas at a high price.
00:53Seen from space, this formation is distinguished
00:55by huge rays of matter spreading over more than 150 km
00:59and remaining still luminous.
01:01Their presence suggests that a colossal impact occurred at this place.
01:05A historical testimony evokes an unusual event on this subject.
01:08In 1178, five monks, then on a trip to Canterbury in England,
01:13would have observed a strange phenomenon on the Moon.
01:16According to them, it seemed to be sinking,
01:19accompanied by flames and sparks.
01:21Shortly after, the darkness would have engulfed the entire surface.
01:25In the 20th century, scientists put their hands on these archives
01:29and assumed that these monks had observed the formation of the Giordano-Bruno crater.
01:34However, it was later discovered that this crater
01:37was about 4 million years old.
01:39Fortunately, because such an impact, if it had really occurred in the 12th century,
01:43would have caused a real chaos on our planet,
01:46causing a gigantic storm of meteors.
01:49Anyway, our HO3 is probably a fragment of the detached Moon
01:54during this impact 4 million years ago.
01:57Fortunately, there is no need to panic.
01:59When astronomers detected this lunar fragment,
02:02they quickly traced its orbit.
02:04It turns out that it will not hit us in the near future.
02:07It will be our quasi-satellite for at least 3 more centuries,
02:12which means that it will follow a trajectory around the Sun,
02:15remaining close to the Earth without colliding.
02:18Its orbit, however, remains chaotic.
02:21It seems to follow a circular movement around our planet
02:24with constant oscillations, approaching and moving away,
02:28ascending and descending.
02:29And in the 24th century, its movement will become even more erratic,
02:33adopting an iron-horse orbit that will gradually move it away.
02:37Could HO3 one day collide with Earth?
02:41Maybe.
02:42But such a scenario could occur in millions of years,
02:45when it could leave its current orbit to collide with Earth, Venus or even the Sun.
02:51It could also be totally ejected from the solar system.
02:54Although it is one of the closest asteroids ever observed,
02:58it remains one of the smallest and most stable.
03:01This discovery also opens up fascinating perspectives
03:04concerning life in the universe.
03:06It appears that rocks can travel between celestial bodies.
03:10Some advance the hypothesis that life could spread across the universe
03:15by traveling on these rocks, like a space taxi.
03:18Or, at least, the essential elements of life, like carbon.
03:22Maybe life even arrived on our planet by making stops on rocks from Mars.
03:27Although HO3 probably does not carry life,
03:30the fact that it can travel for millions of years,
03:33carrying matter while remaining intact, reinforces this theory.
03:37Astronomers plan to send a device to study HO3.
03:41In 2017, a group of students suggested using a space ship for this.
03:46The Chinese National Space Administration
03:49plans to send a robotic probe to HO3 around 2025.
03:54This probe should go there, collect samples,
03:58then bring them back to Earth for analysis.
04:00Unfortunately, this asteroid is invisible to the naked eye.
04:03With a diameter of just 130 meters,
04:06it would be too small and too weak to be observed without a powerful telescope.
04:10However, there is another asteroid that will be visible,
04:13and promises to be impressive.
04:15In 2029, a large asteroid will pass so close to Earth
04:20that it will be visible to the naked eye.
04:22Do not miss this event,
04:23because it is a unique occasion in a period of 1000 years.
04:27This asteroid, known as 2004 Mn4,
04:32or Apophis for short,
04:34is much larger than HO3,
04:36with a diameter of about 370 meters.
04:39This passage will be the closest ever recorded.
04:42This asteroid had caused some panic in December 2004,
04:46because there was a 2.7% probability that it would hit Earth in 2029.
04:52Fear then seized many people.
04:55The very name, Apophis,
04:57refers to the evil serpent of Egyptian mythology,
05:01a gigantic creature fighting the god Ray
05:03and constantly seeking to swallow the sun to destroy the world.
05:07Fortunately, thanks to more precise data,
05:09scientists have quickly found that it would indeed pass very close to us in 2029,
05:15but that it would only pass without causing any damage,
05:17like a quiet pebble.
05:19Another concern, however,
05:21was linked to the possibility that Apophis would cross a hole in the gravitational lock
05:25during its passage close to our planet.
05:27This could have accidentally changed its orbit.
05:30And if such a phenomenon occurred,
05:32it would return to Earth in 2036,
05:35a bit like the planet in the movie Melancholia.
05:38However, after new calculations,
05:40researchers have ruled out this hypothesis.
05:43Apophis will still approach Earth in 2036,
05:47but at a distance equivalent to that of Venus when it crosses our planet.
05:51After that, Apophis and Earth will follow their respective trajectories.
05:56On average, an asteroid the size of Apophis hits the Earth about once every 80,000 years.
06:01If such an impact occurred,
06:03it would destroy a vast area,
06:05causing earthquakes and tsunamis worldwide.
06:08However, it would not trigger an apocalypse.
06:11Far from it.
06:12Apophis will only be visible in Europe,
06:14Africa,
06:15and Western Asia.
06:17So, if you want to observe it,
06:19you may not have to travel.
06:21The asteroid will appear like a star moving quickly in the night sky,
06:25and will shine enough to be observed with the naked eye.
06:29It will be relatively easy to spot at night,
06:31although the lights of the cities can complicate its observation.
06:35Consider for a moment that these asteroids are not the only ones to hang around.
06:39So much so that HO3, Capophis are part of the Apollo-class asteroids.
06:43This group of asteroids has trajectories that cross those of the Earth.
06:48They are thus a real threat.
06:50Because by crossing the Earth's orbit,
06:53they could potentially approach our planet,
06:56or even collide with it.
06:58The first asteroid of this group to be observed
07:01is Apollo 1862,
07:03named after the Greek god of the sun.
07:06Discovered in 1932,
07:08it is from him that the group takes its name.
07:10This asteroid is even more imposing.
07:13It measures more than 1 km wide.
07:15It is so large that it even has a small moon in its orbit.
07:18In addition,
07:19Apollo does not only cross the Earth's orbit,
07:22but also that of Venus and Mars.
07:25Funny little fact.
07:26Although it was the first asteroid of this type to be identified,
07:30telescopes have accidentally lost sight of it for more than 40 years.
07:34Scientists have therefore simply continued to census the visible asteroids.
07:39When Apollo was rediscovered in 1973,
07:43it was no longer on the list
07:45and had to settle for a much higher number.
07:48Apollo will continue to pass near the Earth over the next centuries.
07:52In 2075,
07:53it will be somewhere around Venus.
07:56However,
07:57it should spend 100 hours.
07:59In any case,
08:00there is nothing to worry about.
08:02Because astronomers closely monitor these asteroids.
08:05If there was an immediate danger,
08:07we would probably be informed.
08:09For an asteroid to completely destroy life on Earth,
08:12it should have a diameter greater than 10 km.
08:15Like the one that contributed to the extinction of dinosaurs,
08:1866 million years ago.
08:20However,
08:21these asteroids are so extraordinarily rare that by the time they arrive,
08:25it is possible that humanity
08:27has already colonized other planets.
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