UNIVERSITY PARK, Pa. — “I'm going to try to convince you that we live in a bit of a special time, where some of the questions that we have asked for millennia are now actually within our reach,” said Suvrath Mahadevan, Verne M. Willaman Professor of Astronomy and Astrophysics in the Eberly College of Science at Penn State.
Mahadevan gave the first of two short lectures to open the 2026 Ashtekar Frontiers of Science lecture series at Penn State University Park last month. This year’s lecture series is exploring how researchers in the Eberly College of Science approach some of today’s biggest societal and scientific questions using different approaches, highlighting the breadth of multi-disciplinary research in the college.
Mahadevan’s talk focused on the search for potentially habitable planets beyond our solar system. Planets where scientists might one day find signs of life showing that humans are not alone in the universe and maybe even help bring understanding to the origins of life. He explained that the idea of a habitable zone, a region around a star where liquid water could exist on a planet, meaning it could potentially support Earth-like life, was developed by Penn State Evan Pugh Professor James Kasting in the 1990s.
“Earth does have a twin — Venus,” Mahadevan said. “It is roughly similar in size to Earth, but one is a tropical paradise and the other is completely shrouded with carbon dioxide, hydrogen sulfide clouds and toxic rain. It’s one of the hottest objects in the solar system. It's just a little bit too close to the sun.”
Mahadevan described how he and his colleagues search for planets outside Earth’s solar system that might occupy the habitable zone around their stars using instruments designed and built at Penn State. The very first of one such exoplanet was discovered by Alex Wolszczan, Atherton Professor and Evan Pugh University Professor Emeritus at Penn State, Mahadevan said. Now, with hundreds of known exoplanets, Mahadevan described efforts underway to characterize their size, orbits and atmospheres.
“In our lifetimes, we have gone from not knowing any planets outside the solar system to actually knowing many, and we are well on our way to searching for life on some of these planets,” Mahadevan said.
In the second talk, Tom Stewart, assistant professor of biology, discussed his research using fossils and comparative biology to understand how human ancestors made the transition to life on land.
“Life began about 3.5 billion years ago in the ocean,” Stewart said. “We think it evolved once — a single origin — and every living thing, all the plants, all the animals, all the bacteria, you and me, are all the result of billions of years of evolution, of slow change, of diversification, of speciation. And that's a really incredible thing.”
Stewart specifically studies how vertebrates, animals with backbones, made this transition to life on land. He said that for the group of animals called the tetrapods — those with four limbs, fingers and toes, which includes birds, reptiles, amphibians and mammals — the transition occurred only once.
“You may be noticing that you are not underwater,” Stewart said. “We've made a major transition in the history of this lineage and we're not the only ones to have come to live on land. Our own lineage made this transition about 375 million years ago.”
He described fossil hunting trips to the Arctic where the exposed rock dates to about 375 million years ago, when it would have been located close to the equator. There Stewart and his colleagues have found several specimens of a fossil fish called “Tiktaalik” that helps fill a gap in the fossil record between fish with fins and animals with limbs, which were likely first used to push along the ground in shallow water.
Stewart also described his research with mudskippers, small living fish that spend some time out of water, to understand another important adaptation to life on land — blinking.
“We are part of an unbroken chain of living creatures that extends back 3.5 billion years,” Stewart said. “And if you want to understand that history, if you want to understand the way that you are, it's important to pick apart all the complexity of that to explain exactly how it happened in history. In our lab that involves the fossil record, looking directly at how this might have happened by studying rocks spread all over the Earth, and also understanding the commonalities in the physiology, anatomy, genetics of living species and bringing those things together to have a better sense of where we came from.”
A recording of Mahadeven’s and Stewart’s talks is available on the college’s website along with other previous Ashtekar Frontiers of Science talks.
There are four lectures remaining in this year’s series. The next lecture, to be held at 11 a.m. on Feb. 7 in 001 Chemical and Biomedical Engineering Building, will focus on questions around climate and feature Helen Greatrex, assistant professor of geography and of statistics, and John Harlim, professor of mathematics. More information can be found on the Ashtekar Frontiers of Science website.