Other planets could have even more life than Earth does, scientists say

'This is a surprising conclusion'

Other worlds could be filled with even more flourishing life than we have on Earth, scientists have said.

The new study could have significant implications for the way we search for alien life. It also suggests that search could be more likely to find life on exoplanets than we had thought.

"This is a surprising conclusion", said lead researcher Dr Stephanie Olson. "It shows us that conditions on some exoplanets with favourable ocean circulation patterns could be better suited to support life that is more abundant or more active than life on Earth."

In recent years, scientists have found huge numbers of exoplanets, or worlds orbiting around stars that are not our own. But they are all very far away – impossible to reach even with the fastest space probes, and difficult even to see in any detail.

Researchers are working on a variety of ways to learn about those worlds, including telescopes that will be able to "sniff" their atmospheres and learn more about what the planets could be made of. But to understand the information that comes back, scientists need to build detailed and complicated models of how planets form and their climates work.

By combining those observations with those models, scientists aim to understand which of those distant planets could be home to alien life.

Now Dr Olson and her team have combined that work to understand the conditions on those exoplanets, which will help inform that search. The work was presented at the Goldschmidt Geochemistry Congress in Barcelona.

"NASA's search for life in the Universe is focused on so-called Habitable Zone planets, which are worlds that have the potential for liquid water oceans," she said. "But not all oceans are equally hospitable – and some oceans will be better places to live than others due to their global circulation patterns".

To conduct the study, the team made models of those planets using Nasa software, which allows them to simulate the conditions on those exoplanets. Using that Nasa technology, they were able to create models of the possible climates and oceans that could be on those exoplanets.

They found that many of them seemed like more hospitable and flourishing places for life than even Earth is. They looked at the process in Earth's oceans that allows life to take root down here – and considered whether that same process could be happening elsewhere in the universe.

"Our work has been aimed at identifying the exoplanet oceans which have the greatest capacity to host globally abundant and active life," said Dr Olson in a statement.

"Life in Earth's oceans depends on upwelling (upward flow) which returns nutrients from the dark depths of the ocean to the sunlit portions of the ocean where photosynthetic life lives. More upwelling means more nutrient resupply, which means more biological activity.

"These are the conditions we need to look for on exoplanets".

By modelling a variety of different exoplanets, the researchers were able to think about which types would be most likely to develop and then sustain life. And they were surprised to find that Earth is not the best kind – and that there may be other worlds out there that are a far better place for life to begin.

"We have used an ocean circulation model to identify which planets will have the most efficient upwelling and thus offer particularly hospitable oceans," she said. "We found that higher atmospheric density, slower rotation rates, and the presence of continents all yield higher upwelling rates.

"A further implication is that Earth might not be optimally habitable – and life elsewhere may enjoy a planet that is even more hospitable than our own."

The work is important because our technology means that we are unable to see everything: there is almost certainly more life than we will ever be able to see, even with the most advanced telescopes and other equipment. That means scientists will need to optimise their search by looking at the planets where life will find it easiest to find a home.

"We expect oceans to be important in regulating some of the most compelling remotely detectable signs of life on habitable worlds, but our understanding of oceans beyond our solar system is currently very rudimentary," said Chris Reinhard, from the Georgia Institute of Technology, who wasn't involved in the study. "Dr Olson's work represents a significant and exciting step forward in our understanding of exoplanet oceanography."

The new research could now help inform how new telescopes are built, since we now know what kinds of planets will be best to search for. "Now we know what to look for, so we need to start looking," said Dr Olson.