Could Alien Life Thrive in Acid Instead of Water?

During the pandemic summer of 2020, with the basketball courts and soccer fields in Concord, Mass., closed and no summer jobs to be had, Max Seager, 17, got to work recreating Venus on his front porch.

His mother, the prominent planetary scientist Sara Seager, was then a professor at M.I.T. and was considering designing a probe to send to Venus. She asked Max to find out how various metals and ceramics would fare when subjected to sulfuric acid, a highly corrosive chemical that engulfs the planet in the form of thick clouds.

He quickly found the relevant information online — platinum, for instance, was known to hold up well in sulfuric acid. But where was the fun in that? Max wanted to see the acid in action.

Perhaps most associated with mobsters dissolving bodies in bathtubs, sulfuric acid is so restricted that Max could buy it only in 30-milliliter bottles. He obtained dozens of them, along with protective gear and ceramic dishes in which to submerge materials.

Then he did what a teenager in possession of acid is wont to do: He put an ant in it.

“The poor ant kind of just liquefied,” Max said. “That led into this bigger series of experiments.”

Next, he dropped in a rhododendron leaf. Curiously, nothing happened. The leaf’s waxy coating kept it from breaking down. This got mother and son thinking. If some organic matter is stable in sulfuric acid, maybe it could survive on Venus or other acid-drenched worlds.

Scientists and science fiction authors have long pondered just how alien actual aliens might be. One big question is whether life on other planets could be made of a primary element other than carbon, the essential building block of all earthly biomolecules. Another is whether the complex chemistry of life could happen in a liquid other than water. And if so, what kinds of extraterrestrial life-forms might arise in this alternative primordial soup.

For decades, though, scientists examining the evidence have come to a rather imagination-deflating conclusion.

“I am, reluctantly, a self-confessed carbon chauvinist,” the astronomer Carl Sagan wrote in “Cosmos” in 1980. Carbon is both abundant in the universe, he explained, and readily forms the large, complex molecules needed to construct the components of living cells.

“I am also a water chauvinist,” Dr. Sagan added, for he could think of no other liquid nearly as suitable for facilitating reactions between organic molecules. Hydrofluoric acid might do, he suggested, except that it is made from fluorine, which is too rare to produce the acid in sufficient quantities. Ammonia is abundant, but it’s a liquid only on cold planets that lack the energy to get chemical reactions going.

Thus, the modern-day search for extraterrestrial life focuses exclusively on finding watery worlds. Astronomers point their telescopes at planets orbiting in the “habitable zone” around their stars, an area where the temperature allows water on a planet’s surface to be liquid rather than vapor or ice.

But studies published over the last three years by the Seagers and their collaborators indicate that there is another clear, stable and abundant liquid in the cosmos that has been overlooked as a possible elixir of life.

“Maybe we should also be looking for sulfuric acid,” Max said.

The researchers’ findings suggest that this infamous liquefier of ants, mafia victims and other earthly organic material could be the benign solvent for a fundamentally different kind of biology.

Seeking Sugar-Free Stability

Max left home in the fall of 2021 to study chemistry at the nearby Worcester Polytechnic Institute, but he and his mother continued their experiments on sporadic weekends and during summer breaks. She got her hands on an old spectrometer, a machine that uses light to probe the structure of molecules, and set it up in their living room. Together they investigated what kinds of organic molecules are stable in sulfuric acid.

“Some people are just born understanding stuff,” Dr. Seager said. “For me, math was easy. For Max, it’s the same with organic chemistry.”

Eventually, they moved their work from the living room into the lab — she at M.I.T., he at W.P.I. — and roped in more collaborators. In 2023, their team reported that the molecular “letters” of DNA — adenine, thymine, guanine and cytosine — which spell the genetic code of all organisms on Earth, remained intact in sulfuric acid.

DNA normally falls apart in sulfuric acid, and the findings suggested the reason: Those genetic letters line up along a backbone of phosphate and sugar molecules, and sulfuric acid eats away at sugar vigorously. The internet is rife with videos of people pouring sulfuric acid into cups of sugar and watching black foam emerge.

The 2023 study meant that some kind of sugar-free version of DNA would do just fine on a sulfuric acid-based world.

Then, last year, the team reported that a possible alternative to DNA did indeed stay intact when immersed in sulfuric acid at room temperature. This version uses chains of amino acids called peptides as its backbone instead of sugars. And in September, Dr. Seager’s team reported that peptides in the acid folded into stable three-dimensional structures, as biomolecules must do to perform their functions.

It now seems that “the stability of organic molecules in sulfuric acid is a rule, not an exception,” said Janusz Petkowski, a collaborator of Dr. Seager’s based at Wrocław University of Science and Technology in Poland.

Aside from sugars, all the major molecules of earthly life hold up in this alternative solvent. So, somewhere out there, life almost as we know it could have swirled together in sulfuric acid ponds.

Could Life Lurk on Venus?

If acid-based life really exists, astronomers might someday find it in the same orbital neighborhoods where they’re already looking for watery worlds around other stars. Sulfuric acid is liquid between about 50 and 639 degrees Fahrenheit, a similar but more extended temperature range than that of liquid water.

For now, though, water remains the priority in astronomers’ search for life. Compared with sulfuric acid, it’s easier to detect on other planets, at least using the current technique of analyzing starlight that filters through a planet’s atmosphere as it passes in front of its star, a method that Dr. Seager coinvented in 2000. To find water, we can look for water vapor in a planet’s sky, whereas sulfuric acid barely evaporates.

“It’s worthwhile to look at alternative solvents,” said Vikki Meadows, an astrobiologist at the University of Washington in Seattle and the NASA-funded Virtual Planetary Laboratory. But Dr. Meadows is focused on what we can detect now. “So, I’m still Team Water for that reason,” she said.

Ever-better telescopes will be built, methods will change and evidence of an acid-drenched world might eventually show up. The objective would then be to study the planet for chemical signs of life, such as the gaseous byproducts of alien metabolisms.

On Earth, the dominant metabolic process is photosynthesis, in which plants and algae harvest sunlight to build sugars, flooding the sky with oxygen. On an acid planet, sugar falls apart, so photosynthesis can’t occur or must work very differently.

“I like this quote a lot from ‘Jurassic Park,’ from Dr. Ian Malcolm,” Dr. Petkowski said. “‘Life finds a way.’”

But he thinks it’s too soon to discuss exactly how acid-based life might power itself, or to contemplate what these life-forms might be like. The chemical possibilities are too novel.

Dr. Seager, who recently moved from M.I.T. to the University of Toronto, has a long-shot hope of finding acid life closer to home.

Venus’s surface is too hot for sulfuric acid seas, but clouds of acid droplets waft in the cooler sky above. It’s possible, she and others said, that these droplets contain Venusian microbes.

Dr. Seager is planning a series of Venus missions in partnership with Rocket Lab, a space company, to gather more data.

Her son Max keeps up with the continuing research on sulfuric acid but is no longer involved, as he is now studying brain cancer in graduate school at the University of Calgary. His mother hopes he’ll return to astrobiology someday, at least as a side gig.

“It was a really good way to spend time together,” Max said.