Alien Land?

Danakil is one of the most unforgiving places on Earth. During the day, for example, temperatures soar to 53oC (127oF).

Emerald-green pools dot the area. They might look beautiful, but they’re filled with water so acidic it would start to eat away at the skin of your toe if you were to dip it in too long. The acidic ponds are caused by volcanic activity in the region. Danakil lies in an area where a tectonic plate—a large, slow-moving rock slab that makes up Earth’s crust, or outer layer—is being pulled apart. That allows hot rock and gases from deep underground to rise toward the surface (see Cracking Up).

“When water mixes with volcanic gases, the ponds become acidic,” says Richard Wunderman, a former volcanologist at the Smithsonian Institution in Washington, D.C. He says that pond water trickles into cracks in the ground, mixing with sulfur dioxide bubbling up from below. This creates sulfuric acid that causes a dramatic decline in the water’s pH—a measure of how acidic a substance is. The lower the pH of a substance, the more acidic it is.

Danakil is one of the most brutal places on Earth. For example, daytime temperatures soar to 53oC (127oF).

Emerald-green pools dot the area. They might look beautiful, but their water is extremely acidic. Dip your toe in too long, and it would start to eat away at the skin. The acidic ponds are caused by volcanic activity in the region. Danakil lies in an area where a tectonic plate is being pulled apart. That’s a large, slow-moving rock slab that makes up Earth’s crust, or outer layer. The movement allows material from deep underground to rise toward the surface (see Cracking Up).

“When water mixes with volcanic gases, the ponds become acidic,” says Richard Wunderman. He’s a former volcanologist at the Smithsonian Institution in Washington, D.C. He says that pond water trickles into cracks in the ground. It mixes with sulfur dioxide bubbling up from below. This creates sulfuric acid that causes the water’s pH to drop. The pH is a measure of how acidic a substance is. The lower the pH, the more acidic the substance is.

“These are not exactly ideal conditions for life,” says Gómez. He explains that the pH for all living processes is in the neutral range, a pH of 6 to 7.5. Danakil’s ponds reach extremely acidic pH levels of 0 to 2, he says. That’s about the same level of acidity as vinegar.

Not only is the water acidic, it’s also boiling hot. When water seeps deep underground, it makes contact with magma, or liquid rock beneath Earth’s surface. The superheated water then gushes back into the ponds through cracks called hydrothermal vents. This heats the ponds to about 40oC (104oF). They’re like steamy, toxic hot tubs.

You’d think nothing could survive such harsh conditions, but Gómez says Danakil’s unique geology makes it the perfect place to hunt for extremophiles. “Its heat, acidic pools, and tectonic activity mean there are several physical and chemical parameters that can be studied,” he says. “These conditions are completely different from the conditions that human beings live in, but they might be optimal for some extremophiles.”

“These are not exactly ideal conditions for life,” says Gómez. He explains that the pH for all living processes is in the neutral range. That would be a pH of 6 to 7.5. Danakil’s ponds reach extremely acidic pH levels of 0 to 2, he says. That’s about the same level of acidity as vinegar.

The water isn’t just acidic. It’s also boiling hot. When water seeps deep underground, it makes contact with magma. That’s liquid rock beneath Earth’s surface. The superheated water then gushes back into the ponds through cracks called hydrothermal vents. This heats the ponds to about 40oC (104oF). They’re like steamy, toxic hot tubs.

You’d think nothing could survive such harsh conditions. Not so, says Gómez. Danakil’s unique geology makes it the perfect place to hunt for extremophiles. “Its heat, acidic pools, and tectonic activity mean there are several physical and chemical parameters that can be studied,” he says. “These conditions are completely different from the conditions that human beings live in, but they might be optimal for some extremophiles.”

Although this region has long interested scientists, Gómez and his team were among the first to research life here. Danakil has remained largely unstudied because of conflicts in the area. “We had to be escorted by soldiers with machine guns wherever we went,” Gómez explains. But he says the danger was worth the risk. He was able to study a special place found nowhere else on Earth.

Gómez and his team took samples from the pools, hydrothermal vents, and mineral deposits around the Danakil region. Samples from the hot acidic pools contained extremophiles. Each has evolved specialized structures within its cell membrane—the protective layer that surrounds a cell. These structures act as pumps to constantly remove acidic substances from the cells so the microbes can maintain a neutral pH within. The microbes’ acid pumps are more powerful and numerous than those of microorganisms that live in environments with a lower acidity, says Gómez.

Scientists have been interested in this region for a long time. But Gómez and his team were among the first to research life here. Danakil hasn’t been studied much because of conflicts in the area. “We had to be escorted by soldiers with machine guns wherever we went,” Gómez explains. But he says the danger was worth the risk. He was able to study a special type of place found nowhere else on Earth.

Gómez and his team took samples from pools, hydrothermal vents, and mineral deposits. Samples from the hot acidic pools contained extremophiles. Each one has certain structures within its cell membrane—the protective layer that surrounds a cell. These structures act as pumps. They constantly remove acidic substances from the cells. That way, the microbes can keep a neutral pH inside. Other microbes in less acidic environments also have acid pumps. But Gómez says the Danakil microbes have more, and theirs are more powerful.

He also found that Danakil’s extremophiles produce more of a specific family of proteins—large biological molecules that carry out essential roles within organisms—than the average microbe. This family of proteins protects cells against damage when they’re exposed to high temperatures or radiation—high-energy waves or particles—from the sun or outer space.

Gómez says that understanding these adaptations could tell scientists more about how life is possible on other planets. In these far-off places, acidity, heat, and radiation levels could exceed those on Earth.

He found another difference between Danakil’s extremophiles and the average microbe. The extremophiles make more of a certain family of proteins. Proteins are large biological molecules that carry out important roles in living things. This family of proteins protects cells against damage from high temperatures. It also protects them against radiation—high-energy waves or particles—from the sun or outer space.

Gómez wants to understand these adaptations. He says this could tell scientists more about how life may be possible on other planets. Acidity, heat, and radiation levels there could top those on Earth.

Scientists call places on Earth that mimic the extreme environments of other planets extraterrestrial analogs. “Just in the past 10 years, we’ve come to find that there are more and more potentially habitable environments in our solar system,” says Linda Billings. She is a consultant to NASA’s Astrobiology Institute, an organization that studies places in the universe that could be home to alien life. Billings explains that scientists are searching all over Earth for unique new analogs to expand the boundaries of where we believe life can exist (see Extreme Earth).

Billings says the discoveries in Danakil could help NASA identify planets with similar features that could be home to extraterrestrial life. “Some of the things we look for on other planets are plate tectonics and hydrothermal systems, like we see in places like Ethiopia,” she explains. “The more we learn about the conditions in which life on Earth can survive, the more we learn about which extraterrestrial environments are worth exploring.”

Some places on Earth seem like the extreme environments of other planets. Scientists call these places extraterrestrial analogs. “Just in the past 10 years, we’ve come to find that there are more and more potentially habitable environments in our solar system,” says Linda Billings. She’s a consultant to NASA’s Astrobiology Institute. This organization studies places in the universe where alien life could occur. Billings explains that scientists are searching all over Earth for unique new analogs. This could increase the limits of where we believe life can exist (see Extreme Earth).

The discoveries in Danakil may point scientists in the right direction. Billings says NASA could look for planets with similar features. These places could be home to extraterrestrial life. “Some of the things we look for on other planets are plate tectonics and hydrothermal systems, like we see in places like Ethiopia,” she explains. “The more we learn about the conditions in which life on Earth can survive, the more we learn about which extraterrestrial environments are worth exploring.”