Years ago, Michael and his colleagues at the observatory detected a very distant planet, whose location and atmospheric composition made it suitable for life. They needed more information, so they decided to launch a ship loaded with a rover to this planet, which they named the blue marble. Now, they are celebrating that the landing has been successful and that the first images captured by the rover are already being uploaded to their computer. They hold their breath and, suddenly, terrified, they see how the screen fills with the image of enormous beasts with feathered bodies and fierce appearance, shaking with their heavy steps the surface of the planet on which the rover barely remains. All this might seem like the plot of a futuristic movie, but it’s actually what would have happened if an extraterrestrial civilization had found Earth ago. 100 million years.
In May 1999, the SETI project was launched, aimed at searching for radio signals likely to have been sent from other planets. In 1995, astrophysicists Didier Queloz and Michel Mayor discovered for the first time a exoplanet. This opened an immense range to the search for new worlds. Little by little, a series of techniques were perfected that allow us to calculate the probability that a planet is habitable, but we still can’t find life. Now, what would happen if we did it the other way around? Could there be intelligent beings on other worlds searching for extraterrestrial life and failing to find us?
It is possible that yes. After all, it would be quite egocentric to think that we are alone in the universe. The problem is that the universe is immense and that the search is complicated for some and for others. Therefore, a team of scientists from the Cornell University has carried out a study aimed at checking when it would have been easier to find us from an extraterrestrial planet. And the results are most curious, since it turns out that it could have been much easier to find the Earth when humans still inhabited it. dinosaurs.
The simple, but complicated, search for extraterrestrial life
Once an exoplanet is detected, it is important to take two factors into account to know if it is habitable. On the one hand, it must be in the habitable zone of its star. That is, neither too close for the water to evaporate, nor so far for it to freeze.
In addition, it must have an atmosphere that protects its surface from cosmic radiation, and the composition of said atmosphere should contain gases necessary for life. The latter is analyzed by spectrum measurement. That is, it studies how the light that reaches the planet is blocked. Depending on the gases in it, some wavelengths or others will be blocked, so that the spectrum formed by the light that has not been blocked can give information about what those gases are.
Logically, the fact that these gases are found in a habitable zone does not mean that there is life on the planet with complete security. Probes or robots would have to be sent to study the scenario more closely, as Michael the alien did. Although it is not that simple, because, logically, the first paragraph of this article is nothing more than a simplified dramatization.
Now, if we can measure the spectra of another planet, couldn’t they measure our own from a distant place? alien planet? There is no reason to think not.
A habitability that goes unnoticed
Earth scientists at Cornell University wanted to know how we have been seen from space over the past few million years.
Specifically, they focused on a period known as Phanerozoicwhich started a few years ago 542 million years and continues in our days. Its translation is “visible life”, as it corresponds to the years in which the Earth has been inhabited by non-microscopic life.
This life, in turn, is responsible for the composition of the atmosphere. A composition that has been changing little by little throughout that time. Today we have the climate change driven by humans as the main reason for the change in said composition, but there have been other modifications due to other causes that, although equally suitable for life, would give rise to a very different spectral profile if extraterrestrials investigated us.
Using climate models and data on fossil records, they were able to calculate the spectral signatures of the atmosphere every 100 years. Oxygen levels have varied throughout the Phanerozoic from 15% to 30%. Both limits touch the extremes 13%, in which the fire could not be lit, and 35%, with which the matter would burn so quickly that it would be impossible to make forests grow. We are currently in a healthy twenty-one%. Healthy as far as oxygen is concerned, of course. We leave greenhouse gas levels for many other articles.
The age of the dinosaurs
He 30% It corresponds precisely to the years in which the Earth was inhabited by dinosaurs. It is a very high percentage of oxygen, but it is also accompanied by other gases whose signatures, if we saw them on an extraterrestrial planet, would serve as a very good indication of life.
Specifically, with this study it was seen that the spectral signatures composed mainly of oxygen and methane or ozone and methane They are the ones that could have been most easily related to life. And these predominated ago 100-300 million years, especially in times of dinosaurs.
Therefore, if Michael the alien and his companions had existed, perhaps they would have encountered us. But perhaps they came across a planet full of merciless beasts and decided to take their ships somewhere else. It would have been the smartest thing, there is no doubt about that.