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Comets and interstellar objects could export Earth's life to the Milky Way



For over a century, proponents of panspermia have argued that comets, asteroids, spaceborne dust, and planetoids are spreading life in our galaxy. However, in recent years, scientists have argued that this type of distribution can go beyond star systems and be intergalactic. Some have even proposed fascinating new mechanisms for how this distribution could take place.

For example, it is commonly argued that meteorite and asteroid impacts are responsible for blowing up the material that would transport microbes to other planets. In a recent study, two Harvard astronomers investigate the challenges involved and suggest another means: objects on Earth that collect microbes from our atmosphere and then launch them into outer space.

The study titled "Exporting Rural Life from the Solar System Using Gravitational Earthing Organs", which is to be considered for publication by the International Journal of Astrobiology . The study was authored by Amir Siraj (a Harvard astronomy student) and Abraham Loeb – Frank B. Baird Jr. Professor of Science and the Department of Astronomy at Harvard University.

The theory of lithopanspermy states that life can be shared between planets within a planetary system. Credit: NASA

To disassemble it, there are several versions of the p anspermy theory. There is lithopanspermia, the idea that stones ejected by collisions are responsible for the spread of microbes from planet to planet. Then there is the larger variant, where interstellar asteroids and comets are responsible for the distribution of life between star systems and perhaps even galaxies. Siraj summed it up for Universe Today by email:

"Traditional theories of panspermia assume that planetary collisions can accelerate deposits from the gravitational field of a planet and possibly even from the host star's gravitational field, among other things, these debris are often right small, and provide little protection against harmful radiation for potentially trapped microbes on their journey through space. "

In addition, the traditional approach to treating panspermia requires a process that both microbes embed in rocks, but also provide enough energy to remove them from Earth and the Sola3r system, which is not an easy task as an object must move at a speed of 11.2 km / s to escape Earth's gravity, and 42.1 km / s to escape the solar system.

In contrast, Siraj and Loeb investigated whether e s for long-period comets or interstellar objects (such as & # 39; Oumuamua and C / 2019 Q4 Borisov) would be able to spread life. This would involve these objects entering the Earth's atmosphere, capturing microbes – detected up to 77 km above the surface – and receiving a gravitational spinner that could send them out of the solar system.

Artistic representation of the first interstellar asteroid / comet "Oumuamua". This unique object was discovered on 19 October 2017 by the Pan-STARRS 1 Telescope in Hawaii. Photo credits: ESO / M. Kornmesser

Siraj offers a number of advantages over objects that strike the surface:

"One advantage of a long-period comet or interstellar object that absorbs microbes from the Earth's atmosphere is that they can be quite large (hundreds of feet to several kilometers) and are guaranteed to be expelled from the solar system by driving so close to the earth. This will allow microbes to get caught in corners and edges of the object and be largely shielded from harmful radiation, so they may still be alive when they hit another planetary system. "

To assess this possibility, Siraj and Loeb have evaluated the resistance that the Earth's atmosphere would exert on an interstellar object, as well as the effect of the gravitational spinner. This allowed them to limit the size and energy of objects that could export microbes from the Earth's atmosphere to other planets and planetary systems.

"We then used observed rates of long-period comets and interstellar objects to determine the frequency of our calibration. Expect that such a process took place in the time when life on Earth existed," Siraj added , As a result, over the course of Earth's life (4.54 billion years), approximately 1 to 10 long-period comets and 1 to 50 interstellar objects could export microbial life from the Earth's atmosphere.

Artist & # 39; s impression of The interstellar object Oumuamua experiences outgassing as it leaves our solar system. Credit: ESA / Hubble / NASA / ESO, M. Kornmesser

They further estimated that if microbial life existed over a height of 100 km (mi) in our atmosphere, the number of export events would rise dramatically to about 10 ^ 5 (that's 100,000!) In the course of Earth's life. This work builds on previous research that has shown that interstellar objects are more prevalent in our solar system. Siraj explains:

"An exciting aspect of this paper is that it provides a concrete process for ejecting large stones from the solar system that are loaded with soil microbes. The dynamic processes of these rocks, which are then trapped in other planetary systems, have been reported earlier. Therefore, this article effectively closes the circle for a concrete process by which life could be transferred from Earth to another planet. "]

When the next interstellar object passes through our system, we should naturally ask," Does this object carry the seed of life into another star system? " By the way, we should ask ourselves if that's how life on earth started billions of years ago. If interstellar objects are the means by which microbial life spreads, in the coming years it should be the top scientific priority to send a mission to intercept and investigate one!

Further reading: arXiv


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