Morgan Cable doesn’t know what life on other planets might look like. That doesn’t keep her from daydreaming.
As Cable said, she and others in the astrobiology community are “agnostic” as to how extraterrestrial life could appear.
“Maybe it’s not going to be small cells,” she said. “Maybe in a Titan lake one cell is one lake and life exists at the interface of where that lake is touching rock. There’s all sorts of weird things that could exist out there, and we have to keep our minds open to it.
“Otherwise we might miss it.”
Not “missing it” is all part of Cable’s job description. As an astrobiologist at the NASA Jet Propulsion Laboratory, the scientist, who will speak Saturday as the second presenter in Wyoming Stargazing’s “World Above the Tetons” series, is examining the conditions on other planets and worlds, like Saturn’s moon Titan, that may support alien life.
She’s also on the hunt for life itself. So far it hasn’t been found anywhere else in the galaxy.
“We’re still searching,” Cable said.
Scientists are also still debating what constitutes “life” and what doesn’t, in the event that researchers find something that might fit the bill. But Cable said coming up with a “specific” answer to that question wasn’t necessary to continue the search.
“You don’t have to be strict with a definition like that,” she said.
After getting her doctorate Cable worked as a project science systems engineer — essentially a liaison between engineers and scientists — on the Cassini mission, which explored the Saturn system for 13 years and discovered that Titan had a liquid water ocean as well as a dense, calm atmosphere similar to Earth’s.
Now, she’s a co-investigator on NASA’s New Frontiers mission, Dragonfly, a project that will send a rotorcraft lander mission to Titan to collect samples, investigate how far chemistry that may precede life has progressed and, potentially, search for signs of water- or hydrocarbon-based life.
That mission won’t land until 2034, but, when it does, Cable and the Dragonfly team will be searching for the three things that always accompany life on Earth: water, chemistry and energy.
“The question is: ‘If you have those three things somewhere else, like on a moon around Saturday or Jupiter, is biology just like the natural evolution of a system, or is it really incredibly unique and are we are terribly, horribly alone?’” Cable said.
Exploring moon worlds is a different approach than searching for life on other Earth-like planets but the astrobiologist is searching places like Titan for a reason. Planets like Earth are not “incredibly common” in the universe.
Our sun is a yellow dwarf, which is much brighter than the most common type of star in the galaxy, red dwarfs. Those stars are so dim viewers on Earth’s surface can’t see them without a specialized telescope.
Cable said planets orbiting red dwarfs are more likely to resemble moon worlds and, since red dwarf systems vastly outnumber solar systems like ours, it’s likely that there are more Titan-like planets than Earth analogues.
Understanding Titan would give astrobiologists a leg up on studying similar worlds.
“Let’s say that we do find conditions for life on Titan, whether on its frigid surface or down in its liquid water ocean,” Cable said. “Our chances of finding life elsewhere could go way up.”
Studying distant worlds with less sunlight — or starlight — than Earth means searching for life different from what we observe on our home planet, where the vast majority of life is sustained by the sun. In outer planets the situation is different. There, Cable said, “sunlight is not the biggest game in town when it comes to energy.” In places like Titan the scientist is interested in chemical energy and geothermal energy sources, environments that, on earth, support only microbial life and small organisms that are good at getting by on the bare minimum.
But that doesn’t mean she’s limiting her search for life and its preconditions to those sorts of organisms. She could imagine a complex organism that consumes massive amounts of energy and lies dormant for long periods, a lifestyle that wouldn’t require as much energy as the constant stream of life on Earth.
“The one thing that I’ve found is that, as a scientist, things always surprise you,” Cable said. “When you’re wrong, that’s when you tend to make the most interesting discoveries.”
The theory of hibernating moon creatures is, of course, all speculation. Life has not been found on other planets. As cosmologist and author Carl Sagan said, “Life is the hypothesis of last resort,” meaning that all other explanations of a suspected abnormality on another planet must be ruled out before life is considered.
Cable follows that maxim but said asking whether life exists on other planets is worth it.
“You have to be more rigorous than you have to for any other field,” Cable said. “For all of these life questions you have to understand the context. You need to understand the environment, otherwise you’re not going to know if life is there or if it’s just some weird chemical reaction.
“And so by asking the question you have to answer all the other questions first.”
And for Cable, asking that question isn’t all about science. It’s also about the greater, existential question that has followed scientists since the search for life began: Are we alone?
“I really hope it’s not that, but either way, we need to know. That’s the point of being alive: to ask questions and then go find the answers.” ￼