LHS 1140b: The first atmosphere detected on a rocky habitable-zone exoplanet

**Sarah Al-Ahmed** (0:04)
The first atmosphere on a rocky exoplanet in a habitable zone, this week on Planetary Radio.
I'm Sarah Al-Ahmed of The Planetary Society, with more of the human adventure across our solar system and beyond. For the first time, scientists have detected an atmosphere on a rocky world orbiting in the habitable zone of another star. This week, I'm joined by the lead author on that discovery, Collin Cherubim, a NASA Hubble Fellow at the University of Chicago. Then, Bruce Betts, our chief scientist, joins me for What's Up, where we're going to dig into the very first detection of an exoplanet atmosphere ever and its surprising connection to this week's guest. If you love Planetary Radio and want to stay informed about the latest space discoveries, make sure you hit that subscribe button on your favorite podcasting platform. By subscribing, you'll never miss an episode filled with new and awe-inspiring ways to know the cosmos and our place within it.
One of the greatest questions humanity has ever asked is whether or not we're alone in the universe. Is there life beyond our planet? To truly get at the heart of that question, though, we need to understand the conditions under which life arose on our own planet and then search for those conditions elsewhere among the stars. It's true that there could be other circumstances under which life can thrive, perhaps in the subsurface liquid water oceans of an exomoon, or maybe in situations that we haven't even fathomed. But for now, we only have one example of a world that's teeming with life, our Earth. If we could find a similar world out there in the vastness beyond our Solar System, it would be extraordinary. As of the date of this recording, humanity has confirmed 6,333 exoplanets, worlds orbiting stars beyond our Solar System. And there are thousands more candidates waiting for follow-up observations. But the vast majority of these worlds are nothing like Earth. We've found hot Jupiters, mini-Neptunes, lava worlds, rogue planets, endless permutations of possibilities out there orbiting other stars. But a world like our own? That's something that we've yet to see.
The search is still ongoing, but it took a major leap forward with the world that we're about to discuss today. The exoplanet is called LHS 1140b. It's a super-Earth, about one and a half times the size of our planet, and roughly five and a half times its mass. It orbits a small, cool red dwarf star about 49 light-years away in the constellation Cetus. It's not only a rocky world, but it orbits in its star's habitable zone, just the right distance that liquid water could conceivably exist on its surface. We don't yet know whether or not it has an ocean, but each new piece of evidence makes this world more and more intriguing. And now we know something else. It actually has an atmosphere, a layer of gas shrouding it that can insulate and protect its surface.
When researchers observed LHS 1140b, they didn't find an atmosphere that's like Earth's, but they did find an atmosphere of helium, the second most abundant element in the universe. As our guest is going to explain, that helium can tell us a great deal, not only about this world, but perhaps about the evolution of rocky worlds with atmospheres. To walk us through how this discovery happened and what it means, I'm joined by the lead author on this paper, Dr. Collin Cherubim. He's a NASA Hubble Fellow at the University of Chicago, who recently completed his PhD at Harvard. His team's paper is called, Helium Escaping from the Atmosphere of a Nearby Rocky Exoplanet Orbiting in a Habitable Zone, and it was published in the journal Science on July 16th, 2026
Hey, Collin. Thanks for joining me.

**Collin Cherubim** (4:04)
Hey, Sarah. Thanks for having me here.

**Sarah Al-Ahmed** (4:06)
And congratulations on your PhD. I understand that just happened recently.

**Collin Cherubim** (4:11)
Yeah. Thanks so much. Yeah. I just finished up at Harvard University, the Earth and Planetary Science Department in May.

**Sarah Al-Ahmed** (4:17)
So you've had one of the most unusual paths in astrophysics that I've kind of come across as I've been interviewing people, right? You got a chemistry degree, you were a professional drummer, a high school teacher, and then off to get all of this science, all this background in exploring worlds.
How did that long winding road lead you to hunting atmospheres on other worlds?

**Collin Cherubim** (4:42)
Yeah, I suppose it was a bit unusual.
The truth is, one day I went to my gym in Boston when I was a high school teacher, and the guy working behind the counter said, hey, what's your favorite element? I said, what? I kind of did a double take, like is he talking to me? I was like, chemical element? He said, yeah. I said, well, it's funny you ask me, because I'm a chemistry teacher. And so I told him it was carbon, which I know some people will think is a cop out, but I mean, you can't really beat carbon.