Scientists have made a surprising finding: some exoplanets have better conditions for life to thrive than Earth. According to Stephanie Olson, lead author of the new study, the conditions on some exoplanets with favorable ocean circulation patterns 'could be better suited to support life that is more abundant or more active than life on Earth.'
Olson presented the findings at the Goldschmidt Geochemistry Congress in Barcelona. She said that the focus of her search was aimed at oceans: '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. 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 develop computer simulations of climate, ocean habitats and other likely conditions on different types of exoplanets, Olson used software developed by NASA’s Goddard Institute for Space Studies.
'Our work has been aimed at identifying the exoplanet oceans which have the greatest capacity to host globally abundant and active life,' Olson said. '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.' She added that these are the conditions her team looked for on exoplanets.
Olson’s team set out to model different types of exoplanets to figure out which of them had higher changes of life developing and thriving.
'We have used an ocean circulation model to identify which planets will have the most efficient upwelling and thus offer particularly hospitable oceans. 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.'
Olson added that because of the limitations of technology, there is likely to be more life than can be detected. As for the search for extraterrestrial life, a subset of habitable planets should be targeted – ones that have large, globally active biospheres. Life will be easiest to detect there, she said.
While it’s too early to test this hypothesis because we do not yet have the telescopes that can identify appropriate exoplanets, Olson hopes that her team’s work will influence future telescope design so that they have the right capabilities. 'We know what to look for, so we need to start looking,' she concluded.
Exoplanets were first discovered in 1992, and more than 4,000 have been confirmed to date, with many more expected to be found by the newest technology. The vast distances to exoplanets mean that it is impossible to reach them with space probes, so scientists use computer modeling to run simulations based on observations made with telescopes. Currently, the exoplanets in the habitable zone – that is, those within a certain range of distances from a star that would keep its oceans liquid – are of particular interest to scientists, as those planets are most likely to harbor life.
Little is known about oceans outside of our solar system. Olson’s work is a step forward in understanding exoplanet oceanography – and, possibly, in our search for life outside of our solar system.