The Discovery That Proved Scientists Wrong | ESA Rosetta Philae

molecular cloud from which the Sun would have originated. Oxygen was an unexpected find, as it is highly reactive and, if there is hydrogen around, it will usually join together to form H2O. Philae also detected carbon and hydrogen in the comet's tenuous atmosphere. The dust particles you see here are small, the largest one collected was only 2mm in diameter, but interestingly it is particles like these that light up the sky during a meteor shower here on Earth. However, what these views give us is an idea of ​​the material that formed the solar system, so we can see where our solar system evolved from.

Comets tend to be very dark and only reflect 3% to 4% of the sunlight that falls on them, which perhaps wouldn't be expected from something that is considered icy. But in reality, not much of a comet's ice is directly exposed to the surface; most of the comet is covered by this layer of complex carbonaceous dust, which is darker than asphalt. These colored sections in this time-lapse show exposed water ice; As you can see, it's not a very large percentage of the comet itself. Unreflected light is absorbed, heating the volatile material beneath the dust layer, causing the outgassing of water and carbon dioxide, which also launches the tiny dust particles that Rosetta collected into space.

As these are ejected at escape velocity, they fall behind the comet and form its tail. Zooming out a bit and looking at comets in general, let's talk about why comets have two tails. A tail follows the orbit of the comet and this tail is the dust tail. The dust tail lights up when sunlight reflects off it. The other tail is made up of volatile material, water and carbon dioxide that outgassed the comet. This tail follows the direction of the solar wind, and these particles light up through ionization and interactions with charged particles from the Sun. Comets are often difficult to see with the naked eye on Earth, but occasionally a comet sheds enough material that it is visible. .

In the Northern Hemisphere, the last bright comet I saw was Hale Bopp in 1997 when I was just a child, but I also recently saw Comet Neowise in 2020. What an amazing sight it was! You people in the southern hemisphere have had a little more luck with comets: you had Comet McNaught in 2007 and Comet Lovejoy in 2011. Going back to 67P, there was another very important reason why the Rosetta-Philae mission occurred in first place, and that was to see if water from comets is the source of water on Earth. Before this mission, the theory was that Earth was bombarded by comets in the early stages of its development, when the solar system was much more chaotic.

Considering that a large portion of comets are water ice, these could have given the Earth's surface the water we enjoy today. But according to Philae's findings, this was not the case. Scientists were able to determine this from the ratio of deuterium to hydrogen in water vapor, which is significantly different from that on Earth. Deuterium is an isotope of hydrogen to which a neutron is added. The ratio of deuterium and hydrogen in water is key to determining where in the Solar System an object originated. Here is the ratio of the Earth and here is the ratio of 67P.

As you can see, they are very different. Only two comets have had water vapor directly measured for deuterium, 67P and Halley's Comet, and neither suggests that comets were the source of water on Earth. Instead, these data give more weight to models that suggest that asteroids are the source of water on Earth, although their water content is generally very low. But maybe there was more water on them billions of years ago? Maybe we just don't see as much water now because all the volatiles from the asteroids have already burned up? In any case, it seems that the Earth would have gone through difficult times during its formation.

Rosetta and Philae were also equipped to detect whether the comet had a magnetic field. Initially,

scientists

believed they had discovered the presence of a magnetic field in the comet, whose "buzz" they converted into audio sound. This is what it sounds like! However, it turns out that this was not the result of a magnetic field, as Philae was unable to detect the presence of a magnetic field on the surface, but rather this sound is the interaction of the solar wind with the comet's atmosphere. In fact, due to this interaction, the comet's atmosphere and nucleus are completely devoid of any magnetic field, which is called a diamagnetic cavity.

Rosetta ended its mission by crashing into the surface of the comet. As the comet moved away from the Sun, there was no guarantee it would have enough power for its heaters, so to maximize the science gained, mission controllers ordered it to make a controlled descent inside the comet. During this descent, it took multiple images that you can see in this time lapse, providing better resolution images of the comet than ever before, until it finally hit the surface and all communication was lost. Between Rosetta and Philae, they have opened our eyes to what the solar system was like during its formation and provided data that has led and will lead to many discoveries.

We look forward to many more missions like this in the future! Space exploration is getting really exciting! Thanks for watching! Thank you very much, as always, to those who support the channel through Patreon and to those who like and share the videos! I really enjoy making them and your support means I can continue making more in the future! If you liked this video, you'll probably like my other spaceship videos, so check them out! All the best and until next time.