Our search for E.T.s—intelligent or otherwise—just hit an asteroid.
Distant moons and planets were once thought to go through phases when they were overflowing with water after their young, dim stars heated up and melted their icy surfaces. However, a team of scientists who recently published a study in Nature Geoscience now believe that Earth is an anomaly when it comes to producing the liquid H2O necessary to keep life as we know it flourishing. Emphasis on life as we know it.
Theoretically, if these worlds orbit their stars at just the right distance (aka the “Goldilocks zone”), they should unfreeze into habitable worlds—but many of them never will become habitable.
Using climate models to simulate how frozen planets evolve as their stars go through phases, the team determined that even the most glacial orb would go from snowball to fireball without the atmospheric greenhouse gases found exclusively on Earth. The immense energy needed to melt so much ice would continue to vaporize the water that is so integral to the survival of life forms on our planet (and similar ones if they exist out there). This is why it’s unlikely any future generations will be colonizing Europa or Enceladus, which will become great balls of fire in the killer radiation of a dying sun.
"We find that the stellar fluxes that are required to overcome a planet’s initial snowball state are so large that they lead to significant water loss and preclude a habitable planet," said the team.
Earth is the huge exception. 600-800 million years ago, it was a forbidding, icy wasteland that was eventually melted just enough by the greenhouse gases released by volcanic eruptions. It is these gases that have kept the planet warm enough to inhabit. Unfortunately, our overconsumption of CO2 has been damaging our uniquely balanced climate irreversibly.
Most of us get too excited about extraterrestrials too soon because the media often oversimplifies potentially habitable planets. The description of what should qualify as a habitable zone is often nebulous, which is why scientists urge for more specifics, going beyond just the possibility of liquid water existing on a rocky planet or moon.
For anyone who wants to believe, we still have no idea whether life forms that can withstand frozen wastes or fiery chasms actually exist. Using the Gaian model to theorize the probability of life on other planets and in other galaxies may only be scratching the surface of what could lurk out there in wild space.