We haven't found life on Mars yet, but one researcher believes we might be able to detect evidence of it on planets outside of the solar system within the next quarter of a century.
Sasha Quanz, an astrophysicist at Switzerland's federal technology institute ETH Zurich, made those remarks at a recent opening of the university's new Center for the Origin and Prevalence of Life.
Speaking at a press briefing on Sept. 2, Quanz detailed the technology projects that are now in the works that may enable researchers to finally answer the question whether we are alone in the universe.
"In 1995, my colleague [and Noble Prize laureate] Didier Queloz discovered the first planet outside our solar system," Quanz said during the briefing. "Today, more than 5,000 exoplanets are known and we are discovering them on a daily basis."
There are many more exoplanets waiting to be discovered given that astronomers believe that each of the more than 100 billion stars in the Milky Way galaxy has at least one companion planet. That makes for an enormous number of exoplanets, many of which, Quanz added, are just like Earth and at the right distance from their host stars to enable conditions for life, such as the presence of liquid water.
"What we do not know is if these terrestrial planets have atmospheres and what these atmospheres are made of," Quanz said. "We need to investigate the atmospheres of these planets. We need an observational approach that would allow us to take pictures of these planets."
The briefing took place just one day after the James Webb Space Telescope team released Webb's first direct image of an exoplanet orbiting a distant star: the massive gas giant HIP 65426 b, a planet 12 times the size of Jupiter orbiting 100 sun-Earth distances from its parent star.
The James Webb Space Telescope, which was not built to study exoplanets but to look for the oldest stars in the universe, has already delivered a string of breakthroughs in exoplanet research, including detecting carbon dioxide and water in the atmospheres of several of them. Quanz, however, cautions that Webb, although the most powerful observatory ever put to space, is not quite powerful enough to be able to see the much smaller, Earth-like planets that orbit closer to their stars at distances where liquid water can exist.
"[The HIP 65426] system is a very special system," Quanz said. "It's a gas giant planet orbiting very far from the star. This is what Webb can do in terms of taking pictures of planets. We will not be able to get to the small planets. Webb is not powerful enough to do that."
However, new instruments are already being built with the sole purpose of filling this gap in the James Webb Space Telescope's capabilities. Quanz and his team are leading the development of the mid-infrared ELT imager and spectrograph (METIS), a first of its kind instrument that will be part of the Extremely Large Telescope (ELT). Currently being built by the European Southern Observatory in Chile, ELT, once completed toward the end of this decade, will feature a 130-foot-wide (40-meter) mirror, making it the largest optical telescope in the world.
"The primary goal of the instrument is to take the first picture of a terrestrial planet, potentially similar to Earth, around one of the very nearest stars," said Quanz. "But our long-term vision is to do that not only for a few stars but for dozens of stars, and to investigate the atmospheres of dozens of terrestrial exoplanets."
Quanz admits that the METIS instrument may still not be the one to pick up the signs of life on a planet outside of the solar system. A ground-based telescope, such as ELT, has to contend with the interference of Earth's atmosphere, which skews the measurements of the chemistry of the atmospheres shrouding the distant worlds. And with Webb not being quite up to the task, an entirely new mission will be needed to answer the big question. That mission, Quanz said, is already being discussed under the auspices of the European Space Agency (ESA). Called LIFE (for Large Interferometer for Exoplanets), the mission, conceived in 2017, is currently in its early study phase and has not yet been officially approved or funded.
"[The mission] is considered as a candidate for a future large mission within the ESA science program," Quanz said.
The space telescope would look at a vast amount of promising exoplanets for traces of molecules in these distant planets' atmospheres that could have been created by living organisms.
The new center at ETH Zurich hopes to lay the groundwork for this future mission, Quanz said, and improve our understanding of the chemistry of life and how it affects planetary atmospheres and environments.
"We need to gain deeper understanding about the plausible building blocks of life, the pathways and the timescales of chemical reactions and the external conditions to help us prioritize target stars and target planets," said Quantz. "We need to verify to what extent the traces of life are true bioindicators, because maybe there are other processes that could lead to the creation of the gasses in these atmospheres."
Quantz added that while ambitious, the 25 year timeframe he set himself for finding life outside the solar system is not "unrealistic."
"There's no guarantee for success. But we're going to learn other things on the way," he said.