But how did a lifeless environment on the early Earth supply this key ingredient?

“For 50 years, what’s called ‘the phosphate problem,’ has plagued studies on the origin of life,” said first author , a 91探花 research assistant professor of Earth and space sciences.

The problem is that chemical reactions that make the building blocks of living things need a lot of phosphorus, but phosphorus is scarce. A new 91探花study, published Dec. 30 in the Proceedings of the National Academy of Sciences, finds an answer to this problem in certain types of lakes.

The focuses on carbonate-rich lakes, which form in dry environments within depressions that funnel water draining from the surrounding landscape. Because of high evaporation rates, the lake waters concentrate into salty and alkaline, or high-pH, solutions. Such lakes, also known as alkaline or soda lakes, are found on all seven continents.

The researchers first looked at phosphorus measurements in existing carbonate-rich lakes, including in California, in Kenya and in India.

While the exact concentration depends on where the samples were taken and during what season, the researchers found that carbonate-rich lakes have up to 50,000 times phosphorus levels found in seawater, rivers and other types of lakes. Such high concentrations point to the existence of some common, natural mechanism that accumulates phosphorus in these lakes.

Today these carbonate-rich lakes are biologically rich and support life ranging from microbes to Lake Magadi’s famous flocks of flamingoes. These living things affect the lake chemistry. So researchers did lab experiments with bottles of carbonate-rich water at different chemical compositions to understand how the lakes accumulate phosphorus, and how high phosphorus concentrations could get in a lifeless environment.

The reason these waters have high phosphorus is their carbonate content. In most lakes, calcium, which is much more abundant on Earth, binds to phosphorus to make solid calcium phosphate minerals, which life can’t access. But in carbonate-rich waters, the carbonate outcompetes phosphate to bind with calcium, leaving some of the phosphate unattached. Lab tests that combined ingredients at different concentrations show that calcium binds to carbonate and leaves the phosphate freely available in the water.

“It’s a straightforward idea, which is its appeal,” Toner said. “It solves the phosphate problem in an elegant and plausible way.”

Phosphate levels could climb even higher, to a million times levels in seawater, when lake waters evaporate during dry seasons, along shorelines, or in pools separated from the main body of the lake.

“The extremely high phosphate levels in these lakes and ponds would have driven reactions that put phosphorus into the molecular building blocks of RNA, proteins, and fats, all of which were needed to get life going,” said co-author , a 91探花professor of Earth & space sciences.

The carbon dioxide-rich air on the early Earth, some four billion years ago, would have been ideal for creating such lakes and allowing them to reach maximum levels of phosphorus. Carbonate-rich lakes tend to form in atmospheres with high carbon dioxide. Plus, carbon dioxide dissolves in water to create acid conditions that efficiently release phosphorus from rocks.

“The early Earth was a volcanically active place, so you would have had lots of fresh volcanic rock reacting with carbon dioxide and supplying carbonate and phosphorus to lakes,” Toner said. “The early Earth could have hosted many carbonate-rich lakes, which would have had high enough phosphorus concentrations to get life started.”

Another recent by the two authors showed that these types of lakes can also provide abundant cyanide to support the formation of amino acids and nucleotides, the building blocks of proteins, DNA and RNA. Before then researchers had struggled to find a natural environment with enough cyanide to support an origin of life. Cyanide is poisonous to humans, but not to primitive microbes, and is critical for the kind of chemistry that readily makes the building blocks of life.

The research was funded by the Simons Foundation’s Collaboration on the Origins of Life.

For more information, contact Toner at 267-304-3488 or toner2@uw.edu and Catling at 206-543-8653 or dcatling@uw.edu.

The subsurface ocean of Saturn’s moon probably has higher than previously known concentrations of carbon dioxide and hydrogen and a more Earthlike pH level, possibly providing conditions favorable to life, according to new research from planetary scientists at the 91探花.

The presence of such high concentrations could provide fuel 鈥� a sort of chemical 鈥渇ree lunch鈥� 鈥� for living microbes, said lead researcher a 91探花doctoral student in Earth and space sciences. Or, it could mean 鈥渢hat there is hardly anyone around to eat it.鈥�

The new information about the composition of Enceladus鈥� ocean gives planetary scientists a better understanding of the ocean world鈥檚 capacity to host life. Fifer said.

Enceladus is a small moon, an ocean world about 310 miles (500 kilometers) across. Its salty subsurface ocean is of interest because of the similarity in pH, salinity and temperature to Earth’s oceans. Plumes of water vapor and ice particles 鈥� spotted and studied by the spacecraft 鈥� erupting hundreds of miles into space from the ocean through cracks in Enceladus’s ice-encased surface provide a tantalizing glimpse into what the moon鈥檚 subsurface ocean might contain.

But Fifer and colleagues found that the plumes aren鈥檛 chemically the same as the ocean from which they erupt at 800 miles an hour; the eruption process itself changes their composition. He is working with ESS faculty members and . They will present their work June 24 at the .

Fifer and colleagues say the plumes provide an “imperfect window” to the composition of Enceladus鈥檚 global subsurface ocean and that the plume composition and ocean composition could be much different. That, they find, is due to plume , or the separation of gases, which preferentially allows some components of the plume to erupt while others are left behind.

This in mind, the team returned to data from the Cassini mission with a computer simulation that accounts for the effects of fractionation, to get a clearer idea of the composition of Enceladus鈥檚 inner ocean鈥檚. They found 鈥渟ignificant differences鈥� between Enceladus鈥檚 plume and ocean chemistry. Previous interpretations, they found, underestimate the presence of hydrogen, methane and carbon dioxide in the ocean.

鈥淚t鈥檚 better to find high gas concentrations than none at all,鈥� said Fifer. 鈥淚t seems unlikely that life would evolve to consume this chemical free lunch if the gases were not abundant in the ocean.鈥�

Those high levels of carbon dioxide also imply a lower and more Earthlike pH level in the ocean of Enceladus than previous studies have shown. This bodes well for possible life, too, Fifer said.

“Although there are exceptions, most life on Earth functions best living in or consuming water with near-neutral pH, so similar conditions on Enceladus could be encouraging,” he said. “And they make it much easier to compare this strange ocean world to an environment that is more familiar.”

There could be high concentrations of ammonium as well, which is also a potential fuel for life. And though the high concentrations of gases might indicate a lack of living organisms to consume it all, Fifer said, that does not necessarily mean Enceladus is devoid of life. It might mean microbes just aren鈥檛 abundant enough to consume all the available chemical energy.

The researchers can use the gas concentrations to determine an upper limit for certain types of possible life that could exist in the icy ocean of Enceladus.

In other words, he said: “Given that there’s so much free lunch available, what’s the greatest amount that life could be eating to still leave behind the amount we see? How much life would that support?”

Thanks to Cassini, he said, we know about Enceladus’ ocean and the types of gases, salts and organic compounds that are present there. Studying how the plume composition changes can teach us yet more about this ocean and everything in it.

“Future spacecraft missions will sample the plumes looking for signs of life, many of which will be affected just by the eruption process,” Fifer said. “So, understanding the difference between the ocean and the plume now will be a huge help down the road.”

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For more information, contact Fifer at lufifer@uw.edu.

A new 91探花 study uses the pond’s bizarre chemistry to pinpoint the water’s source. The recent , published Sept. 15 in Earth and Planetary Science Letters, reports that it is fed by a regional deep groundwater system and not, as previously suggested, from moisture seeping down from local valley slopes.

“Don Juan Pond is probably one of the most interesting ponds on Earth,” said lead author , a 91探花research assistant professor in Earth and space sciences. “After 60 years of extensive study, we still don鈥檛 really know exactly where it’s coming from, what drives the fact that it’s visible on the surface, and how it’s changing.”

The perennial pond measures about 100 by 300 meters, the size of a few football fields, and is about 10 centimeters (4 inches) deep on average. It was first visited in 1961 and named after the expedition’s helicopter pilots, Donald Roe and John Hickey, earning it the name Don Juan Pond. The unique salts in the pond lower the freezing point, which is why this saline pond can exist in a place where the temperature ranges from minus 50 to plus 10 degrees Celsius (-58 to +50 F).

The pond was long believed to be fed by deep groundwater. But then a high-profile 2013 suggested that near-surface moisture seeps, similar to features recently observed on Mars, were transporting salts downhill to create the salt pond.

Toner is a geochemist specializing in the formation and properties of water in extreme environments on Earth, Mars and beyond. For the new study, Toner created a model to compute how salty water changes during evaporation, freezing, and with different water and salt inputs and outputs. In Antarctica’s appropriately named , water evaporation concentrates salts in the pond, which forces some salts to crystallize. These processes, along with inputs and outputs, cause the pond’s water to change over time.

Toner ran his model for two situations: one where the water was gurgling up from beneath, and another where it was trickling down from near-surface seeps. Results show that the observed chemical makeup could only be produced from underneath.

“You couldn鈥檛 get Don Juan Pond from these shallow groundwaters,” Toner said. “It鈥檚 definitely coming from the deep groundwater.”

His calculations also show that upwelling groundwater cycles through the pond every six months, meaning the water must exit the pond via some unseen underground outflow.

The pond’s hydrology is important to geologists because nowhere on Earth is more similar to Mars. The Red Planet is extremely cold and dry, and the McMurdo Dry Valleys are one of the coldest and driest locations on Earth.

“If there is water on Mars, it’s probably going to look a lot like this pond,” Toner said. “Understanding how it formed has large implications for where would you expect to find similar environments on Mars.”

Recent studies hint that liquid water might exist on the surface of Mars, potentially harboring life or even eventually supporting long-term human settlements. The darker lines on steep slopes, which look like moisture streaks observed above Don Juan Pond, could be caused by a similar groundwater system.

Toner will be part of a team exploring Don Juan Pond and surrounding areas this December, sponsored by NASA and the National Science Foundation. Researchers will spend six weeks camping near the pond and taking repeated chemical measurements of its liquid. They will also explore the nearby slopes to measure the chemistry of the moisture seeps, and try to find further evidence for the source of salts to Don Juan Pond.

“If we accept that the deep groundwater theory is true, then what we’re seeing could be part of a bigger process that involves quite an extensive aquifer,” Toner said. “When thinking about the implications for a similar environment on Mars, that’s much more exciting than just a localized surface phenomenon.”

The research was funded by NASA. Other co-authors are and in the 91探花Department of Earth & Space Sciences.

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For more information, contact Toner at toner2@uw.edu.

NASA grant: NNX15AP19G