Can board meteors to colonize the universe

Aliens may be heading for meteors to colonize space, study suggests. Here's how we could spot them.

A theory called "panspermia" suggests that life forms can spread to new planets by attracting meteors. New research lays out a road map to finding where these hypothetical planet-hopping aliens might live.

If life can spread from planet to planet, a concept known as "panspermia," then we may find it even if we don't know what we're looking for, new research suggests.

Astronomers search for life beyond Earth. Although there are several promising places in the solar system, the abundance of exoplanets means that we are more likely to find life on a planet orbiting another star. According to NASA, there are more than 5,000 confirmed exoplanets so far, and the number is always growing.

But this search for extraterrestrial life currently faces one major obstacle: We don't know exactly what we're looking for. We know of only one type of planet that is definitely capable of hosting life, and we know of only one type of life - that is Earth and the carbon-based life that occurs here. But life, astronomers say, can take a surprising number of forms across the galaxy. While we may get lucky and find an exact replica of Earth with the exact same life form, we are likely dealing with dark, ambiguous, nuanced situations that will take many years to resolve.

A few astronomers have recently proposed an alternative to this approach, focusing less on what life will look like and more on what life will do. Specifically, they propose a detection strategy based on the concept of panspermia, the idea that life can start on one planet and spread to others by attracting meteorites.

Although panspermia is outside the mainstream of scientific research, it is not pure pseudoscience. Martian meteorites have been found on Earth, and scientists are often amazed by the resilience of living things and the extreme environments in which they can survive.

One of the main characteristics of any form of life is its ability to alter the natural balance of the planet. On Earth, for example, our atmosphere has much more oxygen than it would without life, and distant observers will notice much more green on our land than otherwise.

We don't know exactly what characteristics of an exoplanet would change this alien life, but if this life is capable of panspermia, it will try to make the same changes on every planet it encounters as it spreads from world to world has. Sometimes it would fail if the conditions weren't right for that life to thrive, but sometimes it would succeed, making the new planet similar to its original world. Then this new planet would serve as the starting point for a new round of panspermia.

In their new study, the researchers developed a statistical test where if we measure enough planetary properties, we may be able to identify a group of nearby planets that share similar properties. Since these planets, each orbiting a distant star, would have no other reason to be similar to each other, this group will stand out from the collection of all exoplanets.

Such a discovery would not be a smoking gun for identifying life, but it would be a big clue that something strange is going on with these planets, and that the cause could be the spread of life between stars.

The researchers acknowledged that their work has limitations. First, panspermia is assumed to be possible, which is an untested hypothesis. Second, their technique only works if we can collect enough data on a large number of exoplanets. But the advantage of their technique is that it is "agnostic," meaning it can identify a potential sign of life without making any major assumptions about how that life works.