A team of astrophysicists think they may have cracked a big mystery: how life got here on Earth. Or, they at least have come up with some interesting new ideas.

Research by a team from the Harvard-Smithsonian Center for Astrophysics believe indicates that alien life may have spread like a virus in the universe, eventually making its way to Earth, according to a Discovery News report.

It’s a hypothesis called panspermia, and it may have been the delivery system that allowed alien biology to spread from one star system to the other.

Panspermia describes a process where life is transplanted from planet to planet, jump-started by a huge asteroid impact that causes pieces of a planet’s crust to be blasted into space containing samples of life, which could eventually find their way to another world. This could provide the basis for seeding life in new environments — although it would take a really hardy life form to survive such an event.

It’s not the only theory on how life spread from planet to planet, with “directed panspermia” another popular hypothesis. This is a situation where an intelligent civilization deliberately seeds other star system with capsules that contain its own biological image.

Then there is the idea that freeze-dried dead biology could have made the trip on space rocks, a hypothesis called “necropanspermia.”

Right now it’s all academic hypothesizing — there is no hard evidence for any of these processes. But it’s an interesting guesstimation into how life on Earth unfolded, and scientists do know that chunks of planets can travel to other planets. They have found meteorites on Earth that are known to have come from Mars.