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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
What Would It Take to Say We Found Life?
We call this the podium test. What would it take for you personally to confidently stand up in front of an international audience and make that claim? When you put it in that way, I think for a lot of scientists, the bar is really high.
So of course, there would be obvious things, you know, a very clear signature of technology or a skeleton or something like that. But we think that a lot of the evidence that we might encounter first will be much more subtle. For example, chemical signs of life that have to be detected above a background of abiotic chemistry. And really, what we see might depend a lot on where we look.
On Mars, for example, the long history of exploration there gives us a lot of context for what we might find. But we’re potentially talking about samples that are billions of years old in those cases, and on Earth, those kinds of samples, the evidence of life is often degraded and difficult to detect.
On the ocean worlds of our outer solar system, so places like Jupiter’s moon Europa and Saturn’s moon Enceladus, there’s the tantalizing possibility of extant life, meaning life that’s still alive. But potentially we’re talking about exceedingly small amounts of samples that would have to be analyzed with a relatively limited amount of instrumentation that can be carried from Earth billions of miles away.
And then for exoplanets, these are planets beyond our own solar system. Really, what we’re looking for there are very large magnitude signs of life that can be detectable through a telescope from many light-years away. So changes like the oxygenation of Earth’s atmosphere or changes in surface color.
So any one of those things, if they rose to the suspicion of being evidence of life, would be really heavily scrutinized in a very sort of specific and custom way to that particular observation. But I think there are also some general principles that we can follow. And the first is just: Are we sure we’re seeing what we think we’re seeing? Many of these environments are not very well known to us, and so we need to convince ourselves that we’re actually seeing a clear signal that represents what we think it represents.
Carl Sagan once said, “Life is the hypothesis of last resort,” meaning that we ought to work hard for such a claim to rule out alternative possibilities. So what are those possibilities? One is contamination. The spacecraft and the instruments that we use to look for evidence of life are built in an environment, Earth, that is full of life. And so we need to convince ourselves that what we’re seeing is not evidence of our own life, but evidence of indigenous life.
If that’s the case, we should ask, should life of the type we’re seeing live there? And finally, we need to ask, is there any other way than life to make that thing, any of the possible abiotic processes that we know and even the ones that we don’t know? And as you can imagine, that will be quite a challenge.
Once we have a piece of evidence in hand that we really do think represents evidence of life, now we can begin to develop hypotheses. For example, do we have separate independent lines of evidence that corroborate what we’ve seen and increase our confidence of life?
Ultimately, all of this has to be looked at hard by the entire scientific community, and in that sense, I think the really operative word in our question is we. What does it take to say we found evidence of life? Because really, the answer, I think, depends on the full scientific community scrutinizing and skepticizing this observation to finally say that we scientists, we as a community and we as humanity found life.
[END VIDEO TRANSCRIPT]
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Last Updated Sep 10, 2025 Related Terms
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By Amazing Space
BLOOD MOON TONIGHT! Total Lunar Eclipse September 7, 2025 + 5 Amazing Moon Features You Can See!
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
These maps of Prince George’s County, MD, show surface temperatures collected a few hours apart on July 30, 2023 from the Landsat 9 satellite and the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) instrument. The dark blue spots in the right hand image are likely clouds that formed in the afternoon.Credit: Stephanie Schollaert Uz, NASA Goddard Space Flight Center Thousands of Americans are impacted each summer by excessive heat and humidity, some suffering from heat-related illnesses when the body can’t cool itself down. Data from NASA satellites could help local governments reduce the sweltering risks, thanks to a collaboration between NASA scientists and officials in Prince George’s County, Maryland. The effort demonstrates how local officials in other communities could turn to NASA data to inform decisions that provide residents with relief from summer heat.
NASA researchers and their Prince George’s County collaborators reported in Frontiers in Environmental Science that they used the Landsat 8 satellite, jointly operated by NASA and the US Geological Survey, and NASA’s Aqua satellite, to gain insight into surface temperature trends across the county over the past few decades. The data also show how temperatures have responded to changing land use and construction. It is information that county planners and environmental experts hope can aid them in their attempts to remediate and prevent heat dangers in the future. The collaboration may also help the county’s first responders anticipate and prepare for heat-related emergencies and injuries.
Cooperation with Prince George’s County expands on NASA’s historic role, said Stephanie Schollaert Uz, an applications scientist with NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and one of the study authors. “Applying government satellite data to county-level problems is new here. We’re trying to make it easier for people outside of NASA to use our data, in part by including how-to guides referenced at the end of our paper,” Schollaert Uz said.
In the long run, county officials hope to use NASA satellites to track the negative health impacts that arise from land use and modification. Removal of tree cover and the construction of non-permeable roads, parking lots, and structures that lead to water runoff are among the factors that create heat islands, where temperatures in localized areas soar relative to the surrounding landscape. In addition to the direct dangers of heat for county residents and workers, areas with higher-than-normal temperatures can drive intense local weather events.
“There’s potentially a greater incidence of microbursts,” said Mary Abe of Prince George’s County’s sustainability division. “The atmosphere can become supercharged over hot spots,” causing high winds and flood-inducing rains.
Prince George’s County planners anticipate relying on NASA satellites to determine where residents and county employees are at greater risk, predict how future construction could impact heat dangers, and develop strategies to moderate heat in areas currently experiencing elevated summer temperatures. Efforts might include protecting existing trees and planting new ones. It could include replacing impermeable surfaces (cement, pavement, etc.) with alternatives that let water soak into the ground rather than running off into storm drains. To verify and calibrate the satellite observations crucial for such planning, county experts are considering enlisting residents to act as citizen scientists to collect temperature and weather data on the ground, Abe said.
Eventually, the NASA satellite temperature data could also lead to strategies to curb insect-borne diseases, said Evelyn Hoban, associate director for the Prince George’s County division of environmental health and communicable disease. “Once we know where the higher temperatures are, we can check to see if they create mosquito or tick breeding grounds,” said Hoban, who coauthored the study. “We could then focus our outreach and education, and perhaps prevention efforts, on areas of greater heat and risk.”
A NASA guide is available to aid other communities who hope to duplicate the Prince George’s County study. The guide provides introductions on a variety of NASA satellite and ground-based weather station data. Instructions for downloading and analyzing the data are illustrated in an accompanying tutorial that uses the Prince George’s County study as an example for other communities to follow on their own.
One of the greatest benefits of the collaboration, Abe said, is the boost in credibility that comes from incorporating NASA resources and expertise in the county’s efforts to improve safety and health. “It’s partly the NASA brand. People recognize it and they’re really intrigued by it,” she said. “Working with NASA builds confidence that the decision-making process is based firmly in science.”
By James Riordon
NASA Goddard Space Flight Center
Media contact: Elizabeth Vlock
NASA Headquarters
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Last Updated Aug 28, 2025 EditorJames RiordonLocationNASA Goddard Space Flight Center Related Terms
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By NASA
NASA/Christopher LC Clark The parachute of the Enhancing Parachutes by Instrumenting the Canopy, or EPIC, test experiment deploys following an air launch from an Alta X drone on June 4, 2025, at NASA’s Armstrong Flight Research Center in Edwards, California. NASA researchers are developing technology to make supersonic parachutes safer and more reliable for delivering instruments and payloads to Mars.
The flight tests were a first step toward filling gaps in computer models to improve supersonic parachutes. This work could also open the door to future partnerships, including with the aerospace and auto racing industries.
Image Credit: NASA/Christopher LC Clark
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Ocean currents swirl around North America (center left) and Greenland (upper right) in this data visualization created using NASA’s ECCO model. Advanced computing is helping oceanographers decipher hot spots of phytoplankton growth.NASA’s Scientific Visualization Studio As Greenland’s ice retreats, it’s fueling tiny ocean organisms. To test why, scientists turned to a computer model out of JPL and MIT that’s been called a laboratory in itself.
Runoff from Greenland’s ice sheet is kicking nutrients up from the ocean depths and boosting phytoplankton growth, a new NASA-supported study has found. Reporting in Nature Communications: Earth & Environment, the scientists used state-of-the art-computing to simulate marine life and physics colliding in one turbulent fjord. Oceanographers are keen to understand what drives the tiny plantlike organisms, which take up carbon dioxide and power the world’s fisheries.
Greenland’s mile-thick ice sheet is shedding some 293 billion tons (266 billion metric tons) of ice per year. During peak summer melt, more than 300,000 gallons (1,200 cubic meters) of fresh water drain into the sea every second from beneath Jakobshavn Glacier, also known as Sermeq Kujalleq,the most active glacier on the ice sheet. The waters meet and tumble hundreds of feet below the surface.
Teal-colored phytoplankton bloom off the Greenland coast in this satellite image captured in June 2024 by NASA’s PACE (Plankton, Aerosol, Cloud, ocean Ecosystem) mission.NASA The meltwater plume is fresh and more buoyant than the surrounding saltwater. As it rises, scientists have hypothesized, it may be delivering nutrients like iron and nitrate — a key ingredient in fertilizer — to phytoplankton floating at the surface.
Researchers track these microscopic organisms because, though smaller by far than a pinhead, they’re titans of the ocean food web. Inhabiting every ocean from the tropics to the polar regions, they nourish krill and other grazers that, in turn, support larger animals, including fish and whales.
Previous work using NASA satellite data found that the rate of phytoplankton growth in Arctic waters surged 57% between 1998 and 2018 alone. An infusion of nitrate from the depths would be especially pivotal to Greenland’s phytoplankton in summer, after most nutrients been consumed by prior spring blooms. But the hypothesis has been hard to test along the coast, where the remote terrain and icebergs as big as city blocks complicate long-term observations.
“We were faced with this classic problem of trying to understand a system that is so remote and buried beneath ice,” said Dustin Carroll, an oceanographer at San José State University who is also affiliated with NASA’s Jet Propulsion Laboratory in Southern California. “We needed a gem of a computer model to help.”
Sea of Data
To re-create what was happening in the waters around Greenland’s most active glacier, the team harnessed a model of the ocean developed at JPL and the Massachusetts Institute of Technology in Cambridge. The model ingests nearly all available ocean measurements collected by sea- and satellite-based instruments over the past three decades. That amounts to billions of data points, from water temperature and salinity to pressure at the seafloor. The model is called Estimating the Circulation and Climate of the Ocean-Darwin (ECCO-Darwin for short).
Simulating “biology, chemistry, and physics coming together” in even one pocket along Greenland’s 27,000 miles (43,000 kilometers) of coastline is a massive math problem, noted lead author Michael Wood, a computational oceanographer at San José State University. To break it down, he said the team built a “model within a model within a model” to zoom in on the details of the fjord at the foot of the glacier.
Using supercomputers at NASA’s Ames Research Center in Silicon Valley, they calculated that deepwater nutrients buoyed upward by glacial runoff would be sufficient to boost summertime phytoplankton growth by 15 to 40% in the study area.
More Changes in Store
Could increased phytoplankton be a boon for Greenland’s marine animals and fisheries? Carroll said that untangling impacts to the ecosystem will take time. Melt on the Greenland ice sheet is projected to accelerate in coming decades, affecting everything from sea level and land vegetation to the saltiness of coastal waters.
“We reconstructed what’s happening in one key system, but there’s more than 250 such glaciers around Greenland,” Carroll said. He noted that the team plans to extend their simulations to the whole Greenland coast and beyond.
Some changes appear to be impacting the carbon cycle both positively and negatively: The team calculated how runoff from the glacier alters the temperature and chemistry of seawater in the fjord, making it less able to dissolve carbon dioxide. That loss is canceled out, however, by the bigger blooms of phytoplankton taking up more carbon dioxide from the air as they photosynthesize.
Wood added: “We didn’t build these tools for one specific application. Our approach is applicable to any region, from the Texas Gulf to Alaska. Like a Swiss Army knife, we can apply it to lots of different scenarios.”
News Media Contacts
Jane J. Lee / Andrew Wang
Jet Propulsion Laboratory, Pasadena, Calif.
626-379-6874 / 818-354-0307
jane.j.lee@jpl.nasa.gov / andrew.wang@jpl.nasa.gov
Written by Sally Younger
2025-101
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Last Updated Aug 06, 2025 Related Terms
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