A newly released study from NASA shows Mars had an ancient ocean that might have been as large as Earth's Arctic Ocean. STAR CITY, RUSSIA - MARCH 5: In this handout from National Aeronautics and Space Administration or NASA, Astronaut Scott Kelly is seen inside a Soyuz simulator at the Gagarin Cosmonaut Training Center (GCTC) March 5, 2015 in Star City, Russia. Way Up There space series Can our minds handle it? Hi-seas dome hand out See what it's like to fly over Mars Story highlights New radar detections suggest a subsurface lake on Mars (CNN) — A lake of liquid water has been detected by radar beneath the southern polar ice cap of Mars, according to a new study by Italian researchers from the Italian Space Agency, published Wednesday in the journal Science. Evidence was gathered by the Mars Advanced Radar for Subsurface and Ionosphere Sounding instrument, also known as MARSIS, on the European Space Agency’s Mars Express spacecraft. Between May 2012 and December 2015, MARSIS was used to survey the Planum Australe region, which is in the southern ice cap of Mars. It sent radar pulses through the surface and polar ice caps and measured how the radio waves reflected back to Mars Express. Those pulses reflected 29 sets of radar samples that created a map of drastic change in signal almost a mile below the surface. It stretched about 12.5 miles across and looked very similar to lakes that are found beneath Greenland and Antarctic ice sheets on Earth. The radar reflected the feature’s brightness, signaling that it’s water. “We interpret this feature as a stable body of liquid water on Mars,” the authors wrote in the study. The study authors ruled out any other causes for this brightness, apart from water-rich sediments. “This is just one small study area; it is an exciting prospect to think there could be more of these underground pockets of water elsewhere, yet to be discovered,” said Roberto Orosei in a statement. Orosei is the lead study author and principal investigator of the MARSIS experiment. Previously, there has been some suggestions about water on Mars, like droplets of water condensing on the Phoenix lander or as the possible cause of recurring slope lineae, which are seasonal dark streaks on Martian slopes. But there hasn’t been evidence of stable bodies of water until now, the researchers said. However, the presence of liquid water at the base of Martian polar caps was first hypothesized in a study 31 years ago. Given its location beneath the polar ice cap, the water is expected to be below the freezing point of water. But salts like magnesium, calcium and sodium already found on Mars could help the water to form a brine, which would lower the melting point to allow the lake to remain liquid. On Earth, lakes exist below the Antarctic ice sheet even though the mean annual temperature is around negative 76 degrees Fahrenheit. Brine lakes on Earth can remain liquid at 8.6 degrees Fahrenheit, according to the study. In comparison, salty ocean water freezes at 28.4 degrees Fahrenheit, according to the National Oceanic and Atmospheric Administration. Much like our own ice sheets, the polar ice caps change depending on the climate and act as archives for what has happened in the past. Learning more about these caps can reveal Mars’ climate history. “The long duration of Mars Express, and the exhausting effort made by the radar team to overcome many analytical challenges, enabled this much-awaited result, demonstrating that the mission and its payload still have a great science potential,” said Dmitri Titov in a statement, Mars Express project scientist. “This thrilling discovery is a highlight for planetary science and will contribute to our understanding of the evolution of Mars, the history of water on our neighbor planet and its habitability.” But how reliable are these detections? Outside experts have not been able to confirm these findings with other radar detections, like SHARAD, the Shallow Radar sounder onboard the Mars Reconnaissance Orbiter. “We don’t see the same reflector with SHARAD, not even when we recently summed together [thousands] of observations to create CATSCAN-like 3-D views of both polar caps,” Nathaniel Putzig, Mars Reconnaissance Orbiter SHARAD deputy team leader and senior scientist at the Planetary Science Institute, said in an email. “We’re hoping to carry out that same imaging process with the MARSIS data next. I’m excited to see how the 3-D imaging will clarify the view of this detection and whether we will find similar ones elsewhere beneath the polar caps.”<doc-sep>Just a mile or so beneath the surface, near the south pole of Mars, there is a reservoir of briny water sloshing and churning below layers of ice and rock. This subglacial lake, discovered by a ground-penetrating radar on the Mars Express spacecraft, is about 20 kilometers (12.4 miles) wide and perhaps no more than a meter deep. Its discovery is the latest piece of evidence that suggests water was not only present on Mars in the past but is still flowing in some capacity today. The findings, if confirmed by future observations, would be the most significant discovery of liquid water on Mars to date. Water was not only present on Mars in the past but is still flowing in some capacity today Scientists already had little doubt that there was, at one point, liquid water on Mars, thanks to tiny spherical deposits discovered by the Opportunity rover in 2004 and the comprehensive mineralogy studies conducted by the Curiosity rover. The evidence suggests that vast lakes and rivers dominated the surface of Mars billions of years ago. What's more, tantalizing clues have continued to imply the existence of liquid water on Mars today. Condensation was measured on the Phoenix lander in 2009, and dark streaks spotted on Martian dunes may be evidence of briny water (although more recent examination suggests they could be avalanches of dry sand). This new discovery of a subterranean water deposit, outlined in a new paper in Science, suggests water is indeed underneath the red sands of Mars. Perhaps the Red Planet even has entire subsurface lake systems like those beneath Antarctica. A Breakthrough 15 Years in the Making Mars Express is a European Space Agency probe that has been orbiting the fourth planet from the sun since December 2003. A year and a half after it arrived, the craft deployed two 20-meter radar booms, forming a 40-meter antenna. The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument came online. Since then, MARSIS has been studying Mars with radar signals to learn more about the planet's interior structure and composition. The Mars Express spacecraft with its 40-meter MARSIS antenna deployed. NASA/JPL/Corby Waste In 2007, the instrument detected something interesting. Near the Mars southern polar ice cap, it found strong reflections of radar signals—differences between two layers known as echoes. Strong echoes imply a big difference in what's called dielectric permittivity. There are microorganisms that are capable of surviving well below zero "In the case of Mars, and also in the case of Earth, liquid water is the material that certainly would produce the strongest reflections," says Roberto Orosei, a co-investigator of the MARSIS instrument at the University of Bologna in Italy and lead author of the new study. The strong radar echoes in 2007 wound up being the result of a layer of icy carbon dioxide on the surface of Mars rather than liquid water beneath. "CO 2 ice is very transparent and is able to let the radar pulse penetrate into the ice much better than pure water ice," Orosei says, which is why it mimicked the signal one would expect from underground liquid water. However, he says, many believed the CO2 conclusions "were not the end of the story." Continued observations proved difficult. "The real problem was that observations over the same place in different moments would reveal different results," Orosei says. "So we would see a bright reflection on a certain area one day, and then we would fly over the same area maybe a week later, a month later... and we would not see the same strong reflection we would see ordinarily." Finally, the MARSIS engineers figured out what was thwarting their observations. It was the way their own spacecraft processed the data. "The radar by itself will produce a very high amount of data... [so] it’s necessary to sum together many pulses, more than 100 at a time," Orosei says. This method of averaging the information meant that sometimes the data contained a small, high reflectivity area, while other times it had mysteriously disappeared. "It was something that would really be frustrating in hindsight because we were of course spending years and years debating the possible causes, when in fact the solution really was to change the processing scheme of the spacecraft," Orosei says. Artistic impression of the Mars Express spacecraft probing the southern hemisphere of Mars,superimposed to a color mosaic of a portion of Planum Australe. The study area is highlightedusing a THEMIS IR image mosaic. Subsurface echo power is color coded and deep bluecorresponds to the strongest reflections, which are interpreted as being caused by the presence ofwater. USGS Astrogeology Science Center/Arizona State University/ESA/INAF/Davide Coero Borga Even after this breakthrough, the team spent years taking more observations of the south pole region. Mars Express does not repeat the exact same orbit of Mars, meaning long gaps of time can separate flights over the same area. In addition, the team could gather useful observations only at low altitudes and when the spacecraft was on the night side of Mars because the sun excites the ionosphere of the planet, which blocks radar signals. In total, it took three and a half years to obtain 29 observations of the target location. The scientist who designed MARSIS and who remained most adamant that the signals pointed to a subglacial lake, Giovanni Picardi, passed away during those years. "Professor Picardi... died in 2015, just a few months away from the completion of the data acquisition above the area. So it was really tragic that he could not live to see the end of this work," Orosei says. Even if Picardi wasn't there to see, the MARSIS team realized his dream and revealed a frigid reservoir of liquid water beneath the southern polar ice cap of Mars. The implications for complex systems of subsurface lakes could revitalize the debate about whether microorganisms could exist beneath the surface of Mars to this very day. "It was a long march, a sort of long march through the desert, and we are finally out of it," Orosei says. "It’s like a dark cloud has gone away." Lakes Upon Lakes? The study says the subglacial lake on Mars is cold indeed, and rather salty. Water ice that is near the melting point is opaque to radio waves, and so the ice above the lake must be well below freezing. Accordingly, the subglacial water must be at least negative 10 degrees Celsius. Artistic impression of the Mars Express spacecraft probing the southern hemisphere of Mars, superimposed on a radar cross section of the southern polar layered deposits. The radar cross section has been tilted 90°. The leftmost white line is the surface radar echo, while the light bluespots along the basal radar echo highlight areas of very high reflectivity, interpreted as being caused by the presence of water. ESA/INAF/Davide Coero Borga For this to be possible, the reservoir must be saturated with salts—likely salts of sodium, magnesium, and calcium, which have been discovered on the Martian surface. These salts can reduce the melting point of water to negative 74 degrees C, so the subglacial lake is likely between this temperature and around negative 10 or 20 degrees. "From what I think we have learned about this subglacial lake, the most likely analogue for this environment is the subglacial lake that was recently discovered in Canada... in which the lake itself is in contact with a deposit of salt, and so it is very very salty," Orosei says. Such subglacial lakes on Earth have been shown to support life in some cases. "There are microorganisms that are capable of surviving well below zero even without being in contact with water, and there are microorganisms that can use the salt, presumably the salt in the water on Mars... for their metabolism." The most intriguing possibility is that this Martian lake is not alone, but rather part of an extensive network expanding across the south polar region of Mars. “Data provide some hints that this single lake is not a unique finding," Orosei says. "We do see bright spots in other areas."<doc-sep>Mars hosts a huge underground aquifer of liquid water, according to a group of scientists who say they have found convincing evidence. The underground lake hasn’t been seen directly, but if it’s real, it’s a discovery that substantially increases the likelihood that the Red Planet might host life. Researchers detected the possible reservoir with the Mars Express Orbiter, a European spacecraft that’s been orbiting Mars since 2003. While scanning the ice cap at Mars’ south pole, the probe’s radar instrument, called MARSIS, detected a feature about a mile underneath the surface that was about 12.4 miles wide. The structure has a radar signature that matches that of buried liquid water here on Earth, leading the team to conclude that there’s a lake under the glacier. The researchers say they’ve ruled out all other possibilities for what they’re seeing. “I’ve run out of ideas on how to explain this in a way that isn’t water,” Roberto Orosei, a researcher at Italy’s National Institute for Astrophysics and lead of the team that found the formation, tells The Verge. “We’ve tried to exhaust every possible alternative, and we think we’ve done it.” “Pretty much anywhere there is liquid water on Earth, you find something that’s managed to survive in it.” For decades now, planetary scientists have tried to find liquid water on Mars; most agree that it likely exists in certain regions. This finding, detailed today in Science, is the first indication that water may exist in pools underneath the Martian surface. That has big implications for the search for alien life on our planetary neighbor: bacteria have been found here on Earth in water under glaciers in Antarctica and Greenland. “Pretty much anywhere there is liquid water on Earth, you find something that’s managed to survive in it,” Tanya Harrison, a planetary scientist and director of research for Arizona State University’s Space Technology and Science Initiative who was not involved with this discovery, tells The Verge. An underground reservoir may be the perfect place for Mars microbes to survive as well. However, the idea of liquid water under the surface of Mars is sure to be hotly debated. Today’s finding is only based on radar measurements, which means it’ll be difficult to confirm unless we send more sophisticated instruments to Mars in the future or if we actually drill into the ice. But if there is a lake under Mars’ south pole, that may mean there are even more aquifers we just haven’t detected yet. “This would be the first pocket of water [on Mars], and it begs the question: is that true and are there more of them?” Jim Green, NASA’s chief scientist, tells The Verge. NASA is already fairly certain that some water flows on the Red Planet’s surface. In 2015, the space agency announced that a bunch of bizarre dark streaks seen on Mars were likely made up of salty water. That was the first big confirmation that water exists as a liquid on Mars, which is remarkable when you consider that the planet has an average temperature of -80 degrees Fahrenheit. Salt in the water lowers its freezing point, allowing it to stay liquid in frigid conditions; scientists believe the salt probably comes from Martian rocks. Some scientists have had their doubts about those streaks, too. One team has suggested the streaks are just dark grains of sand rolling downhill. But even if those flows are truly liquid water, they’re not quite habitable. They’re fairly small and thin, and they only appear during the warmer times of the year when it’s possible for the water to exist as a liquid. That means the winter wouldn’t be very hospitable. “On any place on the surface of Mars, even where water appears periodically, a terrestrial living organism would die,” says Orosei. “There would not be conditions for their sustained survival.” “It constitutes the closest thing to a habitat we’ve found on Mars.” That’s what makes this unseen aquifer so exciting: it’s potentially big and stable. It’s far enough underground that it isn’t affected by seasonal changes in the planet’s surface temperature, according to Orosei. It probably contains lots of salts, such as magnesium, calcium, and sodium. And the team thinks that the polar ice on top of the water is creating a lot of intense pressure, which also makes it easier for the reservoir to stay in a liquid state. Increased pressure prevents water from freezing at lower temperatures. So it’s possible this aquifer stays a liquid all year round, which is good news for habitability “It constitutes the closest thing to a habitat we’ve found on Mars,” says Orosei. “It’s the only known place on Mars where a terrestrial microorganism, at least the tough ones, could possibly survive. Though we don’t know for sure.” Orosei and his team collected data from the south pole from May 2012 through December 2015 and then spent an additional two years ruling out all of the possible alternatives for what the MARSIS instrument had measured. It’s likely that other scientists may try to find additional explanations. “The interpretation of it as water, I think a lot of people in the community are going to want to see more beyond just the radar,” Cassie Stuurman, a research and development intern at satellite imaging company Planet, who discovered a huge ice deposit under Mars in 2016, tells The Verge. “The results are consistent with water, but I’d like to see more evidence before we say anything conclusive.” The radar measurements don’t give any good indications of thickness, so we don’t know how deep this lake goes. It could be a deep body of water, or it could be a type of sludge that’s mixed with lots of small rocks. “We shouldn’t have a picture in our head of a lake because we don’t know,” Anja Diez, a geologist at the Norwegian Polar Institute, tells The Verge. “We only know where this water is, but we don’t know anything about the depth really.” Fortunately, we may get some more answers about this area soon. In May, NASA launched a new lander to Mars called InSight, which is designed to probe the interior of the Red Planet and figure out its internal temperature. NASA’s Green says InSight’s heat probe could tell us how much heat is escaping the planet, and whether or not liquid water is even sustainable underneath the South Pole. “That instrument might be able to help us understand that the heat is adequate to keep this water liquid and not frozen,” says Green. “That could illuminate a network of underground aquifers.” InSight isn’t quite enough to truly confirm the existence of the lake — if it is a lake. NASA would need to send a robot of some kind to drill into the ice or send a more powerful type of radar to Mars with more sensitivity than the MARSIS instrument. There are no current plans to send a tool like that on any future Martian spacecraft. But Green says this discovery may lead to conversations about what kind of tool might make sense to send. “There has quite a bit of discussion by NASA and other agencies for doing that,” he says. “This now will have some urgency associated with it.” A more powerful radar may also be able to tease out other potential aquifers under the Mars surface — if they’re there. The south pole reservoir had to be fairly large for MARSIS to pick it up, but a more sensitive instrument could detect even smaller pockets. Finding more of these hidden lakes, especially at lower, warmer altitudes, could greatly influence how we send humans to Mars one day. If there is indeed an aquifer underneath a good landing site, NASA may try to land humans there to drill into the ground and look for microbes. “That could illuminate a network of underground aquifers that would hopefully be more convenient and then aid us in deciding where humans would land,” says Green. “Because [water’s] an important resource we’ve got to have.”<doc-sep>
Tampa (AFP) - A massive underground lake has been detected for the first time on Mars, raising hopes that more water -- and maybe even life -- exists there, international astronomers said Wednesday. Located under a layer of Martian ice, the lake is about 12 miles (20 kilometers) wide, said the report in the US journal Science. It is the largest body of liquid water ever found on the Red Planet. "Water is there. We have no more doubt," co-author Enrico Flamini, the Italian space agency's Mars Express mission manager, told a press conference. Mars is now cold, barren and dry but it used to be warm and wet. It was home to plenty of liquid water and lakes at least 3.6 billion years ago. Scientists are eager to find signs of contemporary water, because such discoveries are key to unlocking the mystery of whether life ever formed on Mars in its ancient past, and whether it might persist today. "This is a stunning result that suggests water on Mars is not a temporary trickle like previous discoveries but a persistent body of water that provides the conditions for life for extended periods of time," said Alan Duffy, an associate professor at Swinburne University in Australia, who was not involved in the study. Being able to access water sources could also help humans survive on a future crewed mission to Earth's neighboring planet, with NASA aiming to send explorers in the 2030s. This particular lake, however, would be neither swimmable nor drinkable, and it lies almost a mile deep (1.6 kilometers) beneath the icy surface in a harsh and frigid environment. Whether microbial forms of life could lie within is a matter of debate. Some experts are skeptical of the possibility since the lake is so cold and briny, mixed with a heavy dose of dissolved Martian salts and minerals. The temperature is likely below the freezing point of pure water, but the lake can remain liquid due to the presence of magnesium, calcium and sodium. Story continues "This is a discovery of extraordinary significance, and is bound to heighten speculation about the presence of living organisms on the Red Planet," said Fred Watson of the Australian Astronomical Observatory. "Caution needs to be exercised, however, as the concentration of salts needed to keep the water liquid could be fatal for any microbial life similar to Earth's," added Watson, who was not involved in the research. - Radar detection - The discovery was made using a radar instrument on board the European Space Agency's Mars Express orbiter, which launched in 2003. The tool is called the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS), and was designed to find subsurface water by sending radar pulses that penetrate the surface and ice caps. MARSIS "then measures how the radio waves propagate and reflect back to the spacecraft," said the study. These reflections "provide scientists with information about what lies beneath the surface." A team of researchers led by Roberto Orosei of the National Institute for Astrophysics in Bologna, Italy, surveyed a region called Planum Australe, located in the southern ice cap of Mars, from May 2012 until December 2015. A total of 29 sets of radar samplings showed a "very sharp change in its associated radar signal," allowing scientists to map the outlines of the lake. "The radar profile of this area is similar to that of lakes of liquid water found beneath the Antarctic and Greenland ice sheets on Earth, suggesting that there is a subglacial lake at this location on Mars," said the report. Researchers said they are not sure how far down it goes, but that it may be around three feet (one meter) deep. - Confirmation needed - "This is the first body of water it has detected, so it is very exciting," David Stillman, a senior research scientist in the Department of Space Studies at Southwest Research Institute in San Antonio, Texas, told AFP in an email. However, Stillman, who was not involved in the research, said another spacecraft, or other instruments, need to be able to confirm the discovery. He noted that a higher-frequency radar instrument made by the Italian space agency SHARAD, on board the Mars Reconnaissance Orbiter launched in 2005, has been unable to detect subsurface water. "It is strange that SHARAD cannot confirm this discovery. In fact, SHARAD cannot penetrate through the ice here and no one understands why it can't," Stillman said. "This suggests that something strange is going on here.