Is there life outside our planet? This is one of the most important questions of humanity. Perhaps the “aliens” are already living with us and that is why we are ruining our lives with the constant ridiculous political decisions or perhaps it is the fake meat of the big mac who knows? What is certain is that we are still looking for life outside our planet.
So far, more than 4,200 exoplanets have been discovered outside our solar system. This has been thanks to past techniques for searching for “life” on exoplanets, none of which have tried to search for complex, non-technological life like vegetation. Now, space telescopes will soon be able to directly view these planets, including one within the habitable zone of Earth’s closest neighboring star. This will be possible with the help of these telescopes and a team of researchers in the University of Northern Arizona.
In an attempt to find some answers, the team turned to one of the most common multicellular life forms on Earth: trees. More specifically, its shadows.
«The Earth has more than three billion trees, and each one casts shadows differently to inanimate objects … If you go out at noon, almost all the shadows will be human or plant objects and there would be very few shadows at this time of day if there would be no multicellular life. ‘ said Doughty, the lead author of the paper and an assistant professor at the School of Informatics, Computing and Cybernetic Systems.
The team hypothesizes that trees cast shadows at high solar angles, distinguishing them from single-celled life.
“The hard part is that any future space telescope will probably only have one pixel to determine if life exists on that exoplanet,” said Abraham, who worked closely with Doughty on the study. “So the question is: can we detect these shadows that indicate multicellular life with a single pixel?”
Has the search method been tested?
“It was suggested that craters could cast similar shadows to trees, and our idea would not work,” said Trilling, associate professor of astronomy. “So we decided to look at the replica of the moon landing site in northern Arizona where the Apollo astronauts trained for their mission to the moon.”
Drones were used at different times of the day to determine that craters cast shadows differently from trees.
The researchers then turned to the images to determine whether their theory would work on a large scale. Using the POLDER (Polarization and Directionality of Earth’s Reflectance) satellite, the team was able to observe shadows on Earth at different angles to the sun and times of the day. The resolution was lowered to mimic what the Earth would look like as a single pixel to a distant observer as it orbits the sun. The team then compared this with similar data from Mars, the moon, Venus, and Uranus to see if Earth’s multicellular life was unique.
The team found that in parts of the planet where trees were abundant, such as the Amazon basin, multicellular life could be distinguished, but when it came to looking at the planet as a whole as a single pixel, distinguishing multicellular life was difficult.
Where are we headed with this new discovery?
However, the potential that shadow observation brings to the conversation about life on exoplanets could be closer than scientists and researchers have been before. Doughty thinks the technique is still valid in theory: a future space telescope could be based on the shadows found in a single pixel.
“If each exoplanet were just one pixel, we could use this technique to detect multicellular life for decades to come,” he said. “If more pixels are required, we may have to wait longer for technological improvements to respond if there is multicellular life on exoplanets.”
