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>A large reservoir of liquid water has been found deep beneath the frozen surface of Mars near the planet’s south pole, according to a new paper by Italian researchers published in the journal Science. The discovery caps decades of debate over whether such bodies of liquid water exist on Mars today and is sure to fuel speculation about the possibility that life exists on the Red Planet. Water is considered an essential ingredient for life. Mars' south polar ice cap in an image captured the European Space Agency's Mars Express spacecraft. Italian researchers believe a reservoir lies below ice about a mile thick in an area close to the planet's south pole. ESA “I think the chances now of finding a place to look for current life have gone up,” said Scott Hubbard, a professor of astronautics at Stanford University in Stanford, California, who was not involved in the new research. Hubbard, who served as NASA's first Mars program director, called the discovery “thrilling and exciting.” The subglacial lake was detected below a polar region known as Planum Australe by a ground-penetrating radar instrument aboard the European Space Agency’s Mars Express spacecraft, which has been orbiting Mars since 2003. The lake is about 20 kilometers (12 miles) wide and is buried about 1.5 kilometers (1 mile) below the surface, according to an analysis of radar readings made between 2012 and 2015. ESA's Mars Express used radar signals bounced through underground layers of ice to identify a pond of water buried below the surface. ESA “This is just one small study area,” Roberto Orosei, an astronomer at the University of Bologna and the study’s lead author, said in a written statement. “It is an exciting prospect to think there could be more of these underground pockets of water elsewhere, yet to be discovered.” The newfound lake is likely to be extremely cold and salty, according to the research. Those are “not ideal conditions for life to form,” Kirsten Siebach, a planetary scientist at Rice University in Houston, told the Associated Press. But, she added, microbial life has been found in such environments on Earth. Among other extreme environments on our planet, microbes have been found in Lake Vostok, a large subglacial lake in Antarctica. Scientists have long believed that water flowed on Mars billions of years ago, when the planet was hotter, and it's well-established that large deposits of water ice exist there still. Recent research showed that complex organic molecules — the building blocks of life as we know it — are present there. But this is the first time a stable body of liquid water has been detected on Mars. The Italian scientists spent years analyzing the data to make sure the radar readings indicated liquid water — but not everyone is convinced. “I would say the interpretation is plausible, but it’s not quite a slam dunk yet," Jeffrey Plaut, a research scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, who is not involved in the new research, told Science. But Hubbard called the researchers a “careful group” and said he found the new research convincing — and a likely prelude to additional research. “I think this finding will stimulate other science groups" to reexamine radar data of Mars "to see if they missed anything." Additional reporting by Denise Chow WANT MORE STORIES ABOUT MARS? FOLLOW NBC NEWS MACH ON TWITTER, FACEBOOK, AND INSTAGRAM.<doc-sep>On Earth, scientists use the same technique to detect subglacial lakes and other bodies of water beneath thick, Antarctic ice sheets. Starting in May 2012, MARSIS spent more than three years pinging a region at Mars’s south pole with radio waves, producing a grainy image of the landscape beneath. It helps to look at the data yourself. In addition to an illustration that shows how Mars Express studies Mars, the image below features what’s called a radargram, a picture of different materials, molded out of radio waves. The thick, gray line at the top is the planet’s surface. The squiggles below that are a mix of ice and dust. The thread-like boundary below that indicates rock. And those slivers of bright blue, right along that lowest boundary? That’s water. A little oasis below the vast desert. ESA / INAF / Davide Coero Borga “The reflections from the bottom are stronger than surface reflection. This is something that to us is the telltale sign of the presence of water,” explained Roberto Orosei, a scientist at Italy’s National Institute of Astrophysics who led the research, in a video published Wednesday. “This condition on Earth happens only when you observe subglacial water, like in Antarctica.” But Mars is far colder than Antarctica, so how is it possible that this lake, trapped beneath a layer of thick ice, flows with liquid water? Orosei and his colleagues suggest that the lake is brimming with salts. When salts dissolve in water, they lower the temperature at which water freezes, allowing it to stay liquid (or, if you’re tossing salt on the sidewalk before an icy snowfall, kind of mushy). Scientists have previously detected deposits of salts across Mars’s southern hemisphere. Perhaps some of it dissolved into underground reservoirs, producing briny lakes. Orosei said the MARSIS data supports this idea. “The radar data tell us that this water must contain a large amount of salts,” he said. “This is because the ice above it is very transparent, and this would not be possible if the ice was too warm, too close to the melting point.” The thought of a subglacial lake swirling on Mars is thrilling, but scientists will need more evidence beyond radar data to make a definitive claim. “It shows the power of the radar techniques, and gives tantalizing clues about where we might find liquid water today,” said Jeffrey Plaut, a scientist at NASA’s Jet Propulsion Laboratory who works on MARSIS but was not involved in this research. “If the result is confirmed, it would be the largest known occurrence of present-day liquid water on Mars.” Plaut said he and his colleagues are “pursuing additional lines of evidence to test the interpretation” by Orosei and his team. To confirm the finding, humanity would need to make yet another trip to Mars. “Getting there and acquiring the final evidence that this is indeed a lake will not be an easy task,” Orosei said. “It will require flying a robot there which is capable of drilling through 1.5 kilometers [or about 1 mile] of ice, and this will certainly require some technological developments that at the moment are not available.”<doc-sep>
We finally know where all that Martian water has been hiding! This latest epic discovery was achieved using a radar instrument on a Mars orbiter, with Italian scientists finding a huge liquid reservoir hidden 1.5 kilometres (0.93 miles) under the southern polar ice cap, extending 20 kilometres (12.4 miles) across. The researchers say it's a lot like the subglacial lakes trapped beneath the ice of the Arctic and Antarctica here on Earth. And, like our terrestrial subglacial lakes, it might be where we find surprising life. A subglacial lake has long been hypothesised as a likely place to find water on the Red Planet, but probing beneath glacial regions is not an easy task even here on Earth. It's only been in recent years that scientists have used satellites equipped with radar to uncover the mysteries of the hidden waters of our own planet. For the Mars mission, the research team, from a number of institutions in Italy, used similar technology to study Mars' polar ice caps. An instrument designed specifically for subsurface surveys is on board the European Space Agency's Mars Express probe - in orbit around Mars since 2003. The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) uses radar to look for features under the surface of Mars, and has been looking for signs of subsurface liquid water for over 12 years. It was between May 2012 and December 2015 that the research team seriously investigated a 200-kilometre-wide section of the southern ice cap, in a location called the Planum Australe. They took 29 radar profiles of the region, bouncing radio waves deep beneath the surface of Mars, and collecting the return signal on a receiver. It's by measuring changes between the transmitted signal and what returns that scientists study subsurface features. Radar returning through water is returned more strongly, or 'brightly', than radar returning through rock or sediment. This is what the research team found in their radar results: an anomalously bright region in the Planum Australe. Other explanations, such as very cold and pure water ice, or carbon dioxide ice, could also explain a brightly reflective subsurface anomaly like this, but the research team ran simulations and found that the reflectivity profile did not match their results as well as liquid water. But there's one other big problem: the temperature of the body is estimated to sit at around 205 Kelvin (-68.15 Celsius, or -90.67 Fahrenheit). That is far below the point of freezing, even for hypersaline Antarctic lakes, which remain liquid above 260 Kelvin (-13 Celsius, or 8.6 Fahrenheit) thanks to their salt content. But despite this, the water could still hypothetically remain liquid. We know that salts of sodium, magnesium, and calcium are abundant on Mars - they've been found on the surface. If dissolved into the water, and combined with the pressure of the ice cap on top, they could drop the freezing point to below 200 Kelvin (-74 celsius and -101 Fahrenheit). Life has been found in subglacial Earth lakes. It's been previously proposed that a subglacial Martian lake might therefore also harbour life. This discovery reopens that possibility more prominently than ever before. "There is evidence on Earth of substantial microbial life in the waters below the poles - and even microbes that can survive within ice veins," said astrobiologist Brendan Burns of the University of New South Wales, who was not involved with this research. "Whether similar scenarios are occurring on Mars remain to be experimentally established, but this finding of potential liquid water beneath the surface of Mars opens up fascinating areas of space exploration." It is still important to keep our cool on this one. It's extremely possible that the sheer concentration of salt required to keep the water liquid is absolutely hostile to life. We also have absolutely no means of sampling the water at this point, or any point in the near future. But it's a lot more accessible than Europa and Enceladus, the other Solar System candidates in the search for life; and the water itself could yield clues about the climate history of Mars, its hydrosphere, and what may have happened to its long-disappeared ocean. In addition, now that the team has demonstrated its technique, other researchers know how to look for more such reservoirs on the Red Planet. But we're also going to take a moment to squee about the possibility of Martian microbes.