People may have been chasing immortality for millennia, but thanks to recent research, we now know some organisms have actually been alive for thousands of years.

For the last 10 years, over a thousand scientists in 52 countries have been studying carbon deep in the Earth as part of the Deep Carbon Observatory. They've bored holes miles in the ground and ocean floor, pulling up earth samples and the microorganisms that live inside them. And some of those organisms are ridiculously old.

"It does appear that many of these organisms can last for thousands of years," explained Rick Colwell, a microbiologist at Oregon State University.

Conditions are tough deep in the Earth. Many areas are ridiculously hot and have little nutrition. So some organisms stay alive by living very, very slowly.

"These organisms in the subsurface are much slower in how they do things," Colwell told me. He and his colleagues looked at the metabolisms of these organisms and found something surprising.

© Courtesy of the Deep Carbon Observatory

"Those signals say they last for thousands of years without dividing," Colwell explained. "They don't really divide in the ways we're used to ... It's because they're so energy limited."

Thousands or even millions of species of microorganisms underground work this way. They're so small, you'd need a microscope to see them. Unless enough of them are clustered together, of course. Then they look like slime.

They resemble "something grown in your refrigerator that you know you should throw out," Colwell said.

Scientists began studying deep underground life in the early 1900s, but they only really started looking carefully at the subsurface in the 1980s and 1990s, when companies contaminated a bunch of groundwater and needed to bring in microorganisms to clean it up. Over the last 25 years, scientists learned some of these organisms were incredibly old.

© Altiarchaeales, a type of archaea, were found in German sulfidic springs. It's one of the many microorganisms the scientists studied. Courtesy of the Deep Carbon Observatory

Thanks to this most recent study, scientists are learning how ubiquitous these older life forms really are. After looking at their DNA, scientists concluded many of these creatures may harken back to the earliest stages of life.

"If you watch a crime detective show, it's like that," Colwell said, explaining the genetic investigation process.

Their DNA indicate many of these organisms don't need oxygen to survive, a sign their genes developed in the early stages of the Earth. Billions of years ago, oxygen didn't fill the atmosphere, which was composed largely of other gasses like hydrogen instead.

"They have hydrogen to deal with, and they know how to use it," Colwell told me. "It's an ancient capability."

© Courtesy of the Deep Carbon Observatory