There is a theory that The Earth was created by the fall of a comet carrying elements of life on earth, and humans have always been fascinated by comets, but comets are very fast, and it is extremely difficult to catch a comet or land on it. In 2004, a probe called Rosetta took a decade to catch up with a comet and successfully landed on it, unraveling the mystery of the century after exploring the composition of the comet.
ROSETTA
<h1 class="pgc-h-arrow-right" data-track="652" > cradle of life</h1>
5 billion years ago, the solar system was just formed, and several planets close to the sun formed rocky planets and huge gas planets, and the countless remaining asteroids were like lone ghosts, and could only continue to rotate around the periphery of the solar system.
These asteroids were thrown out by the Sun's gravitational pull and turned into countless fragments of frozen gas and dust, some of which stopped at the edge of the solar wind – the Kuiper Belt, home to tens of thousands of comets, and some of which were ejected to the edge of the solar system's gravitational pull – the Oort Cloud, home to tens of trillions of comets.
The outer reaches of the solar system are billions of comets
These comets hold the most primitive material information of the Solar System, but these comets are too far from Earth to be observed up close, but because some comets will accidentally enter the inner solar system under the influence of the Sun's gravity, they have been observed by humans, especially the short-period comets that exist in the Kuiper Belt.
These comets can even be observed with the naked eye as they pass by Earth, and the most famous of these is Halley's Comet.
Halley's Comet
Halley's Comet, a short-period comet orbiting the Sun for 76.1 years, was the first comet to be recorded by humans, named after British physicist Edmond Halley, who first determined its orbit and successfully predicted a return time. It is also the only comet in a person's life that can be seen with the naked eye at most twice (your lifespan is greater than 76 years).
Edmond Halley
In the most recent time halley comet came back to the solar system in 1986, humans launched four probes in succession to track Halley's comet, and for the first time they took pictures of halley's comet nucleus at close range, at which time people could see clearly that halley's comet nucleus was a 16x8 km stone with cracks in the epidermis, wrinkles and scars, dirty and black, and a mass of about 300 billion tons.
Real photos of Halley's Comet
Comets are mainly composed of water ice and dry ice, and when close to the sun, under the pressure of the solar wind and solar radiation, the water ice inside will melt into gas and eject, which is why the comets we see have a long tail.
Each time Halley's Comet approaches the Sun, it volatilizes 150 million tons of material, so that after about 1 million years, Halley's Comet will cease to exist.
So why is it that comets may carry seeds of life on Earth?
This is because, first of all, comets like Halley's Comet, in fact, the reflectivity of the surface is only 4%, which is lower than the reflectivity of coal, which scientists estimate is to contain a large number of carbon-containing organic molecules, which can be simply understood as (carbon = black), and earth life is carbon-based life, carbon is an indispensable element of life on earth, plus comets have water, oxygen, almost constitute the most important thing in life.
But do comets contain carbon organic molecules, and are they consistent with those on Earth? These can only be figured out if you actually "catch" a comet.
The most feasible method is to launch a probe, carry the instrument to analyze organic molecules, and land on a comet to find out, but this task seems simple, but in fact it is extremely risky.
<h1 class="pgc-h-arrow-right" data-track="688" > rosetta plan</h1>
In 1999, NASA launched the "Stardust" probe, which met a comet called "Wilder 2" in 2004, and the Stardust probe would extend a giant glove made of aerogel to collect the material erupted from the comet from the tail and then install it in the return capsule and bring it back to the ground.
Stardust
This is the first time humans have collected celestial specimens from outside the Earth-Moon system, but unfortunately, this time they have not recovered imaginary organic carbon molecules, because it is likely that these molecules are in the hard shell of the comet.
In 1993, the European Aerospace Agency (ESA) unveiled a bold plan called the Rosetta Program, which would launch a probe into the comet's orbit and orbit the comet.
While maintaining the same speed as the comet, Rosetta will release a lander, land on the surface of the comet, and then analyze the material of the comet's nucleus in situ through the organic molecule analysis instrument on the lander, if the landing is successful, it will be of great help to unlock the origin of life on Earth, which is a very great task.
Release the Rosetta of the login (image)
The name of this mission, rosetta, is named after the Rosetta Stone, in 1799 in an Egyptian port city called Rosetta found a granite stone stele, made in 196 BC, the above three languages are ancient Greek script, ancient Egyptian script and the popular script of the time, and the ancient Egyptian script in it has been lost for thousands of years.
The legendary Rosetta Stone
Through the other texts on this stele, in addition to the lost ancient Egyptian script, this stele made a landmark contribution to the study of ancient Egyptian script. Therefore, ESA also hopes that the probe can solve the mystery of the solar system and even life on Earth like the Rosetta Stone for ancient Egyptian writing, so it is named Rosetta.
Rosetta Stone in the museum
And the lander carried in the probe, named Philai, is a small island in the Nile, there is a Philae temple on the island, which has a Philae obelisk, which has two inscriptions carved with ancient Egyptian characters and ancient Greek scripts, and philologists have studied the ancient Greek script on the Philae obelisk, which has brought great inspiration to determine the ancient Egyptian consonant alphabet.
The island of Philae
So the probe was named Rosetta and the lander was named Philae, which is very meaningful.
Rosetta's main mission is to explore the mystery of the origin of the solar system 5 billion years ago, and whether comets provided Earth with the organic material and water necessary for life.
At the red circle is the lander Philae
There is a sampling system on the Philae lander that drills a 20-centimeter-deep hole in the surface of the comet, collects the samples, and tests the samples in situ, after which the results will be sent to Rosetta, which will then transmit them back to Earth for analysis.
Lander
<h1 class="pgc-h-arrow-right" data-track="709" > task starts</h1>
Rosetta's target is a comet called 46P, a short-period Jupiter family of comets that, like other comets in the Solar System, retains the material from the early days of the Solar System.
Comet 46P
The size of this comet is only 1.2 kilometers wide, so it is very, very difficult to land on such a small comet.
Rosetta was scheduled to launch in January 2003 and join the comet in 2011, but in 2002, the ESA Ariane 5 carrier rocket originally used to launch Rosetta exploded three minutes after launch due to a failed booster during a routine satellite launch mission, and two satellites worth 630 million euros were scrapped.
Launch of a failed Ariane rocket
After the accident, ArianeSpace entered the investigation and evidence collection phase, stopped all launch activities, and the Rosetta, which was originally scheduled to be launched a year later, missed the launch window.
So the ESA turned to another comet called 67P, which was discovered by two Soviet astronomers in 1969, which belonged to the same Comet as Jupiter as 46P, but was larger and heavier.
Comet 67P
The 67P comet is running at a fairly high speed of 130,000 km/h, 108 times the speed of sound, and it is impossible to catch up with such a high-speed comet if it relies on the thrusters on rosetta, so it can only accelerate or decelerate with the help of the planet's gravitational field, also known as gravity assist.
Using Earth, Mars and Jupiter, the gravitational pull of these planets, allowed Rosetta to accelerate and decelerate first,around Comet 67P.
Gravitational slingshot effect
Rosetta in 2005, the use of the Earth's gravity field to accelerate, due to a one-year delay in launch, Rosetta in 2007 flew to Mars, using the gravity field of Mars to slow down, but this deceleration process is very dangerous, only 250 kilometers from the surface of Mars, a little careless will be "aircraft crash".
And during the leap, the probe is completely on the shadow side of Mars, the solar sail panels can not be used, so rosetta must be on standby, in order to restart after the leap, because the probe itself has a limited battery capacity, so once the leap time is too long, the battery will be completely depleted and will not be able to start.
Fortunately, Rosetta lived up to expectations, successfully flew over Mars, and incidentally sent back photos of the Martian atmosphere.
Rosetta photographs Mars
In 2007, Rosetta flew back to Earth, ready to use Earth's gravitational slingshot for a second acceleration, and while crossing the asteroid belt between Mars and Jupiter, encountered an asteroid numbered 2867, 5 kilometers in diameter, and took a photo, which is a diamond-shaped asteroid.
2867
In 2009, Rosetta made its last orbit back to Earth, this time with maximum power close to Comet 67P, and the gravitational slingshot allows the probe to use the gravitational pull between the planets to accelerate again and again to reach the maximum.
In 2010, Rosetta flew over an asteroid called 21 Lutetia, a huge asteroid with a diameter of 100 kilometers, which is also the latest asteroid ever observed by humans, if this asteroid crashed into the earth, the earth would completely become barren, you know, the asteroid that made the dinosaurs extinct is only 10 kilometers in diameter.
Horror 21 Lutetia
In 2014, after a full decade, Rosetta finally came to come to Comet 67P, and it was only then that people really saw what the comet looked like.
This is a comet with a binary star structure, that is, formed by the early fusion of two comets, the size is 4 km x 3 km x 1.3 km, the surface structure is very complex, full of cliffs and cliffs, which is more difficult to land on the comet than the landing asteroid compared to the smooth surface of the asteroid photographed earlier.
The true face of 67P
And the comet is not a soft and fluffy snowball, as people think, but very hard, and the comet will continue to erupt as it approaches the sun, which makes it more difficult to land.
They planned to let Rosetta find a relatively flat position and then lower Philae, so Rosetta began a comprehensive scan of the comet's topography, creating a complete 3D structure.
3D model of 67P
Finally, Rosetta found a suitable landing place, so on November 12, 2014, Rosetta released Philae for landing, and it will land at this location where the comet faces the sun.
Release the lander
The landing site is relatively flat and there is a lot of light to ensure the power supply after Philae, and there are two harpoon-like devices at the bottom of Philae that will be inserted into the surface of the comet nucleus for fixation when landing.
Imaginary landing
Because the escape speed on the surface of the comet is only 1m/s, which means that if a person lands on a comet, it is possible to fly into space with a slight jump and never come back, because the gravitational pull of this comet is too weak, so no one can guarantee that the lander will not bounce back, and the landing can only be successful once, there is no second chance.
During the 7-hour landing process, Rosetta had to fly with the comet all the time, and Philae could not intervene manually during the landing process, relying entirely on the setting of the program.
Finally, after 7 hours of waiting, Rosetta finally sent back the good news that Philae successfully landed on the comet, but the bad news that followed was that Philae's harpoon did not start, which meant that Philae did not land at the intended location.
The first photograph that Philae sent back was a photo of a violent tumbling.
The first photograph transmitted back by the Philae
Later, humans learned that after Philae landed on the surface of the comet, because the surface of the comet was different from what had been previously envisaged, the lander immediately rebounded and then rolled all the way, during which Philae's harpoon has been trying to fix on the surface of the comet, but without success.
Philae has been tumbling on the surface of the comet
According to the data sent back later, the Philae once took off and floated in space, but fortunately the bounce speed was only 38cm/s, and in the 2-hour movement, the Philae rolled into a stone slit and stopped.
The Philae was stuck in a crevice in a rock
It is far from the landing site and cannot receive sunlight, because the Philae has limited power, so after 2 days, the Philae battery is exhausted and the shutdown protection is carried out.
At this point, it was thought that there was still hope, and Rosetta had been flying with the comet, waiting for Philae to wake up.
In June 2015, as the comet got closer to the sun, sunlight also appeared in the slit where Philae landed, so Philae's solar receiver also gained power, restarted and sent back signals.
But the Philae was expected to have less than 60 hours to work, and all the work had to be raced against the clock, and rosetta's later photographs showed Philae landing in a very awkward lying-down manner so that its harpoon launcher was suspended and unable to work.
The Philae lay across the crack
But the surprise was that Philae's sampler was still able to drill holes, which was really great news, and people cheered when they learned about it.
ESA employees
Philae finally spent 2 days to transmit the analytical components back to Earth, through the analysis, the research team found 16 different organic compounds on Comet 67P, which finally proved the previous scientists' conjecture, although organic compounds do not mean necessarily life, but are indeed important substances that make up life.
A photograph of the surface of the comet taken by Philae
At the same time, Philae also found that the comet will be a kind of dusty "snow", which is actually a kind of dust haze, which shows that the comet has a weak atmosphere and a certain atmospheric environment.
Wonderful comet snow
At the same time, Rosetta found organic compounds such as phosphorus and glycine in the dust around comet 67P, and glycine is the key chemical element that makes up DNA and cell membranes, and phosphorus, which was first discovered on comet 67P, is a key element found in all living organisms on Earth, existing in the structural framework of DNA and RNA.
The discovery suggests that it is very likely that comets brought these raw materials that make up life to Earth, helping Earth produce life.
Where does the water on the earth come from, there is a saying that when the early earth first formed, it was bombarded by hundreds of millions of comets carrying water sources, and finally formed an ocean, if the water composition of the comet and the water composition of the earth are the same, then it means that the water we drink now, the water used for bathing, all comes from the comet.
Through the analysis of the dust particles of the comet, Philae found that it contained carbon, sodium, magnesium, aluminum, silicon, calcium, iron, and contained a lot of hydrogen and oxygen, because the comet has always been far away from the sun, so the material above is the composition of the molecular cloud in the early days of the formation of the solar system, representing the material composition of the earliest solar system.
A large number of hydrogen and oxygen elements are the source of liquid water, and liquid water is indispensable for the formation of carbon-based life, so another important task this time is to study whether the water on the comet and the water on the earth are consistent.
After Philae's detection of water vapor on the comet, it was found that the deuterium content of the water on the comet was very different from that on Earth, deuterium is the isotope of hydrogen, so far humans have studied the water vapor of Halley's Comet and Comet 67P, and found that their deuterium content is different from the water on The Earth, which may indicate that the water on the Earth may not come from the comet.
Then all that's left is earth's water coming from asteroid impacts or from Earth's own environment, and even if comets aren't the main source of water on Earth, they still have the potential to send key components of life to Earth.
Philae did all this before the battery ran out, and as the comet moved away from the sun and flew around the comet, Rosetta would also run out of energy, and the ESA decided to make a move to have Rosetta crash, not far from Philae, to keep the two probes together forever and the family always in order.
During Rosetta's final fall, many clear pictures of the surface of the comet's nucleus were taken, until it finally fell on the surface of the comet, and after transmitting the last picture, Rosetta lost contact and stayed on the surface of the comet forever.
The last photo before the Rosetta crashed
So far, the Rosetta mission is perfectly completed, they will continue to run forever with comet 67P, their task is undoubtedly great, bringing more evidence for the origin of human life, we can imagine that in the early days of the birth of the earth, countless comets carrying life material flew to the earth, and finally a comet carried life material, through an extremely complex process to give birth to earth life.
The earth is like a human egg cell, under the impact of billions of sperm (comets), there is finally a combination of life, this seemingly coincidental, more like an inevitability, from human beings to the universe, constantly circulating this process.
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