Recently, I was surprised to see a text from a friend asking if I thought there were aliens living on a nearby exoplanet, K2-18b. As an astronomer who specializes in detailed characterization of planets orbiting other stars, I had THOUGHTS. "Nooooo!!!! This planet is *definitely* not habitable," I wrote back.
The planet in question, K2-18b, orbits a star just 110 light-years away—right next door on cosmic scales. On Wednesday, it was widely reported as a "habitable world." The headlines were prompted by two new studies that detected water in the planet's atmosphere with the Hubble Space Telescope.
Don't get me wrong, this is a very exciting result. K2-18b is the smallest planet where atmospheric features have been detected so far (a monumental technical achievement!), and provides a fascinating window into a planet very different than anything in the Solar System. It's also in the habitable zone of its host star, a region where liquid water could exist on an Earth-like planet.
K2-18b is far from Earth-like, however, and this poses big problems for its habitability. The crux of the issue is the size of the planet. K2-18b is about 2.7 times the size of Earth—so large that the planet must have a massive, extended atmosphere, with a significant fraction of light hydrogen gas. An atmosphere like this makes K2-18b much more akin to Neptune than it is to Earth.
In a hydrogen-rich atmosphere, the temperature and pressure increase the deeper you go. By the time the rocky core is reached, the pressure is expected to be thousands of times higher than the surface of Earth, and the temperature can approach 5,000 degrees Fahrenheit.
These conditions are bad news for the formation of complex molecules, such as DNA, which aren't stable at high temperatures and pressures. Even if we're very open-minded about the conditions required for life to evolve, there's broad consensus that complex molecules of some kind are necessary, to ensure that enough information is provided for replication to occur. Complex molecules cannot form on the deep surface of K2-18b.
So the reporting about this planet and its habitability resulted in a collective freak-out among my colleagues this week and a frantic scramble to communicate with journalists and correct the record. Meanwhile we were all asking: How did so many news outlets get the story so wrong?
It's worth stepping back and looking at the life cycle of science communication. For big results, the cycle begins with a press release put together by scientists and their home institutions. Journalists get advance access to the press release and paper, interview experts on the topic and write up their articles. At every step in this process, there is potential for exaggeration. The result can be like the game of telephone, where a message is whispered from person to person around a circle, and the end result is garbled.
Compounding the situation in this case was fierce competition between two rival scientific groups for credit and attention about the result. Team A led the Hubble observations and had a paper in preparation; Team B downloaded the Hubble data (which was open access) and planned to scoop Team A on the discovery. But then Team A got wind of Team B's plans and rushed to put out their draft first, and so scooped the would-be scoopers. In short, it was a mess, and neither team was primed for coolheaded interactions with the media.
The story started off on the right track in the discovery papers themselves, with clear statements like "the thick gaseous envelope of K2-18b means that it is not a true Earth analogue." But the message started to get distorted in the press releases. The headline for one release read, "first water detected on potentially 'habitable' planet." Another press release opened with the line, "ever since the discovery of the first exoplanet in the 1990s, astronomers have made steady progress towards finding and probing planets located in the habitable zone of their stars, where conditions can lead to the formation of liquid water and the proliferation of life."
Direct quotes from the discovery teams also veered into hyperbole. For instance, the lead author of one paper said, "we know K2-18b has atmosphere and water, making it the best-known candidate for habitability." The leader of the other team described the result as follows: "this represents the biggest step yet taken toward our ultimate goal of finding life on other planets, of proving that we are not alone."
In many news articles on the discovery, the reporters failed to interview any scientists outside the discovery teams who might have offered some crucial perspective. This combination of exaggerated press releases, over-reaching quotes, and the lack of due diligence by some journalists led to an incorrect news story that is spreading like wildfire. My colleagues and I have contacted many news outlets about it, and for the most part they have been quick to respond and amend their stories. But there are too many to correct them all.
The potential consequences of this miscommunication are serious. As David Charbonneau, a professor of astronomy at Harvard, tweeted: "The hunt for atmospheric biomarkers in exoplanets is one of the great scientific opportunities of our time. There is widespread consensus that it will take powerful new observatories. We will not build consensus by confusing the public into thinking we are already doing such work."
Expanding the frontier of knowledge is a challenge. As astronomers, we are seeking objective physical truth, but the practice of doing science is a decidedly human endeavor, with all the accompanying emotion and bias. For the most part, scientists and journalists alike are working hard to make sure the correct information gets out to the public. I'm disappointed that in this case, when the stakes were high, the process failed. We can do better than this.
One day, I believe we will discover water and maybe even signs of life on a truly habitable exoplanet. Let's please not cry wolf so many times before then that the excitement of the discovery is drowned out.