SPACE — The search for life outside Earth has been a hot topic for a long time. One way to detect it is to know what life and our Earth look like when seen from deep space. This article explains how scientists used the Galileo mission for this purpose.
By Brian Koberlein, Universe Today
In the fall of 1989, the Galileo spacecraft was launched into space, bound for Jupiter and its moon system. Given the enormous distance from the king of the planets, Galileo had to take a circuitous tour through the inner solar system, flying by Venus in 1990 and Earth in 1990 and 1992 to get up to speed on reaching Jupiter.
During his flyby of Earth, Galileo took several pictures of our planet, which astronomers used to discover life on Earth. The idea of ’discovering’ life on Earth in the 21st century may seem a bit ridiculous, but the research is quite useful for astronomers looking for life on other worlds.
Because we know the existence of life on Earth and its geography and diversity, images from Galileo can be used as a test to compare with images of exoplanets or planets outside the solar system. Astronomers are still in the early stages of making direct images of some exoplanets, and are still learning what those images might show.
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So, in new work posted to the arXiv preprint server, the research team focused on so-called disk-integrated images. That’s where the light from a planet is taken in its entirety.
A detailed look at Earth vs how it looks as a distant exoplanet. Image:NOAA/NASA/Stephen Kane
Instead of taking detailed images of Earth as above, the team looked at integrated images from the Limited Solid State Imager (SSI). The integrated disk images it collects are similar to images of exoplanets that can be taken with current technology. This means that the image of Earth when viewed as an exoplanet.
They then looked at the overall brightness and spectrum of the images to see how our life on Earth was depicted there. One of the things the authors found was that a lot of the spectral data was erased in the integrated image. This makes it difficult for them to identify certain biosignatures.
The difficulty was to be expected because Galileo’s camera was optimized for Jupiter, which is much farther from the sun and therefore dimmer. However, the team was able to detect oxygen absorption lines, verifying that our planet has an oxygen-rich atmosphere.
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The presence of oxygen doesn’t conclusively prove the existence of life on Earth, but it’s a good start. More interestingly, the team was able to see changes in albedo, or reflective brightness, as the Earth rotates.
From there, they can get a rough idea of the continents and oceans on Earth. Gilileo’s drawings can prove that Earth has a mixture of land and sea, making it suitable for habitation.
2024-02-09 21:22:00
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