Mars Odyssey celebrates 100,000 orbits, captures epic view of solar system's largest volcano

NASA's Odyssey spacecraft, the longest-running mission at Mars, circled the Red Planet for the 100,000th time today, the mission team announced in a statement. To celebrate the milestone, the space agency released an intricate panorama of Olympus Mons, the tallest volcano in the solar system; Odyssey captured the view in March. The volcano's base sprawls 373 miles (600 kilometers) near the Martian equator while it soars 17 miles (27 kilometers) into the planet's thin air. Earlier this month, astronomers discovered ephemeral morning frost coating the volcano's top for a few hours every day, offering fresh insights into how ice from the poles circulates throughout the parched world. In Odyssey's latest image of the volcano, the bluish-white band seen grazing Olympus Mons shows the amount of dust floating in the Martian air when the image was taken, according to NASA. The thin coat of purple just above likely hints at a mixture of atmospheric dust with bluish water-ice clouds. The blue-green layer at the top-edge of the world marks where water-ice clouds reach up about 30 miles (48 kilometers) into the Martian sky, scientists say.

On March 11, 2024, NASA's Odyssey orbiter captured an intricate panorama of Olympus Mons, the tallest volcano in our solar system. (Image credit: NASA/JPL-Caltech/ASU)

To capture the latest panorama, scientists commanded Odyssey to slowly rotate such that its camera pointed toward the Martian horizon, capturing views similar to the kind International Space Station dwellers take of Earth."Normally we see Olympus Mons in narrow strips from above, but by turning the spacecraft toward the horizon we can see in a single image how large it looms over the landscape," Jeffrey Plaut, who is Odyssey's project scientist at the Jet Propulsion Laboratory (JPL) in California, said in the recent news release. "Not only is the image spectacular, it also provides us with unique science data."

By snapping similar images at different times during the year, scientists can study how the Martian atmosphere changes over the planet's four seasons, which last from four to seven months each.

Scientists say the groundwork for the latest image began as early as 2008, when another NASA mission named Phoenix landed on Mars. When Odyssey, which served as a communication link between the lander and Earth, pointed its antenna at the lander, scientists noticed its camera was able to view Mars' horizon.

"We just decided to turn the camera on and see how it looked," said Steve Sanders, who serves as Odyssey's mission operations spacecraft engineer at Lockheed Martin Space in Denver, Colorado. "Based on those experiments, we designed a sequence that keeps [the camera's] field-of-view centered on the horizon as we go around the planet."

The Odyssey mission launched in April 2001 and is managed by JPL. It was NASA's first successful mission to Mars after a pair of failures two years earlier. In 1998, the Mars Climate Orbiter reportedly burned up in Mars' atmosphere after mission engineers mixed up translations between two measurement systems. A year later, the Mars Polar Lander smashed onto the Martian surface due to its engine abruptly shutting off prior to touchdown. Odyssey was therefore widely viewed as a mission of redemption.

Odyssey slid into an orbit around Mars in October 2001, and has since revealed previously hidden water-ice reservoirs just beneath the planet's surface, which may be within reach of future Mars astronauts. The spacecraft also mapped vast swaths of the planet's surface, including its craters, which have helped astronomers decode Mars' history.

The spacecraft's recent milestone of 100,000 orbits means it has covered over 1.4 billion miles (2.2 billion kilometers). The sun-powered spacecraft does not have a fuel gauge, so the mission team relies on their math skills to estimate leftover fuel that keeps the 23-year-old mission running. "Physics does a lot of the hard work for us," said Sanders. "But it's the subtleties we have to manage again and again."

Recent calculations suggest Odyssey has about 9 pounds (4 kilograms) of propellant remaining, which is sufficient to last the legacy mission until the end of 2025.

"It takes careful monitoring to keep a mission going this long while maintaining a historical timeline of scientific planning and execution — and innovative engineering practices," said Joseph Hunt, Odyssey's project manager at JPL. "We're looking forward to collecting more great science in the years ahead."

China's Zhurong Mars rover returns panorama ahead of planetary blackout

China's Mars rover Zhurong has produced a remarkable new panorama of its surroundings in Utopia Planitia to mark 100 days of activity on the Red Planet as preparations continue for the rover to spend more than a month in safe mode this autumn. The six-wheeled, solar-powered rover has covered 3,491 feet (1,064 meters) since rolling onto the Martian surface on May 22. But from mid-September to late October, the rover and its orbiting companion, Tianwen-1, will be in safe mode as the sun's charged particles interfere with their communication with Earth. In preparation for the break, Zhurong paused to take a good look around with its panoramic camera. The returned image shows the rover and its solar arrays and antenna close to a dune, a feature type that mission scientists are keen for Zhurong to analyze. A number of distant features can be seen on the horizon of the panorama including, above Zhurong's antenna, the backshell from the rover's landing in May. Zhurong visited the discarded gear up close in July. Since landing on May 14 and deploying onto the surface a week later, Zhurong has been moving south from its landing platform, analyzing different rocks, dunes and other features as it goes. The Tianwen-1 orbiter with which Zhurong hitched a ride to Mars has been orbiting so that it passes over Zhurong once a day to relay data to mission control in China. The National Astronomical Observatories of China (NAOC) also released an image from Tianwen-1's high resolution camera which shows Zhurong's journey from the lander, including tracks the rover left in the Martian surface.

A panorama of Utopia Planitia returned by the Zhurong rover in late August 2021. (Image credit: CNSA/PEC)

Meanwhile, a new paper on the geological characteristics of Zhurong's landing area identifies a number of features and landforms that scientists working on the mission hope to study as the rover continues south.

A high-resolution image from the Tianwen-1 orbiter showing Zhurong's roving progress through late August 2021.  (Image credit: NAOC)

According to the paper, the rover will investigate transverse aeolian ridges, or dunes, as well as troughs, caused by erosion, and particularly mysterious pitted cones. One of the scientists' key objectives is to use Zhurong's ground penetrating radar to determine the thickness and distribution of Martian soil near some landforms hypothesized to have been created by the presence of subsurface water or ice.

The presence of water would have profound implications for understanding of the climate history of Mars, potential resources for future crewed missions and even as a habitat for simple subsurface life.

The paper also notes that a number of pitted cones are present a number of kilometers to the south of the rover's position. A close-up look at these with Zhurong's terrain camera, multispectral camera, and Mars Surface Composition Detector could help provide fresh insights into how these features were formed, since current hypotheses range from volcanism, mud- or hydrovolcanism, or even underground water flows.

Despite their industry, both Zhurong and Tianwen-1 will soon go into safe mode because of a solar conjunction preventing communications between Earth and Mars. Both spacecraft will pause activities from mid-September through late October, as the sun and the charged particles it releases will obscure our view of Mars from Earth and interfere with radio communications between the two planets. 

A route map showing Zhurong's travels south from its landing platform. (Image credit: BACC)

Both spacecraft will autonomously carry out health assessments, self-monitoring and trouble-shooting until communications can be restored. 

The China National Space Administration and the People's Bank of China also jointly released silver and gold commemorative coins featuring the rover to celebrate Zhurong's 100 days on Mars.

NASA publishes Artemis plan to return Americans to Moon in 2024

Following a series of critical contract awards and hardware milestones, NASA has shared an update on its Artemis program, including the latest Phase 1 plans to land the first woman and the next man on the surface of the Moon in 2024. In the 18 months since NASA accepted a bold challenge to accelerate its exploration plans by more than four years and establish sustainable exploration by the end of the decade, the agency has continued to gain momentum toward sending humans to the Moon again for the first time since the last Apollo lunar mission in 1972. "With bipartisan support from Congress, our 21st century push to the Moon is well within America's reach," said NASA Administrator Jim Bridenstine. "As we've solidified more of our exploration plans in recent months, we've continued to refine our budget and architecture. We're going back to the Moon for scientific discovery, economic benefits, and inspiration for a new a generation of explorers. As we build up a sustainable presence, we're also building momentum toward those first human steps on the Red Planet." In its formal plan, NASA captures Artemis progress to date, identifying the key science, technology and human missions, as well as the commercial and international partnerships that will ensure we continue to lead in exploration and achieve our ambitious goal to land astronauts on the Moon. The agency's powerful new rocket, the Space Launch System (SLS), and the Orion spacecraft are closer than ever to their first integrated launch. The spacecraft is complete while the core stage and its attached four engines are undergoing a final series of tests that will culminate in a critical hot fire test this fall.

Early Artemis Missions
Following a successful hot fire test, the core stage will be shipped to the agency's Kennedy Space Center in Florida for integration with the spacecraft. NASA will launch an SLS and an Orion together on two flight tests around the Moon to check performance, life support, and communication capabilities. The first mission - known as Artemis I - is on track for 2021 without astronauts, and Artemis II will fly with crew in 2023.

In the Phase 1 plan, NASA notes additional details about conducting a new test during the Artemis II mission - a proximity operations demonstration. Shortly after Orion separates from the interim cryogenic propulsion stage, astronauts will manually pilot Orion as they approach and back away from the stage.

This demonstration will assess Orion's handling qualities and related hardware and software to provide performance data and operational experience that cannot be readily gained on the ground in preparation for rendezvous, proximity operations, and docking, as well as undocking operations in lunar orbit beginning on Artemis III.

While preparing for and carrying out these flight test missions, NASA already will be back on the Moon robotically - using commercial delivery services to send dozens of new science investigations and technology demonstrations to the Moon twice per year beginning in 2021.

In 2024, Artemis III will be humanity's return to the surface of the Moon. After launching on SLS, astronauts will travel about 240,000 miles to lunar orbit aboard Orion, at which point they will directly board one of the new commercial human landing systems, or dock to the Gateway to inspect it and gather supplies before boarding the landing system for their expedition to the surface.

Wearing modern spacesuits that allow for greater flexibility and movement than those of their Apollo predecessors, astronauts will collect samples and conduct a range of science experiments over the course of nearly seven days. Using the lander, they will return to lunar orbit before ultimately heading home to Earth aboard Orion.

Work is progressing rapidly on the Gateway. NASA will integrate the first two components to launch - the power and propulsion element and the habitation and logistics outpost - in 2023. This foundation for the Gateway will be able to operate autonomously, conducting remote science experiments when astronauts are not aboard. NASA has selected the first two science instrument suites to conduct space weather investigations in lunar orbit before crew visits.

While NASA has not made a final decision to use the Gateway for Artemis III, Artemis IV and beyond will send crew aboard Orion to dock to the Gateway, where two crew members can stay aboard the spaceship in orbit while two go to the surface. Over time, the outpost will evolve, with new modules added by international partners, allowing crew members to conduct increasingly longer lunar missions.

As detailed in the agency's concept for surface sustainability earlier this year, an incremental buildup of infrastructure on the surface will follow later this decade, allowing for longer surface expeditions with more crew. That concept calls for an Artemis Base Camp that would include new rovers, power systems, habitats, and more on the surface for long-term exploration of the Moon.

Throughout the Artemis program, robots and humans will search for, and potentially extract, resources such as water that can be converted into other usable resources, including oxygen and fuel. By fine-tuning precision landing technologies as well as developing new mobility capabilities, astronauts will travel farther distances and explore new regions of the Moon.

Johnson-Built Device to Help Mars Perseverance Rover Search for Signs of Life

Later this summer, NASA is launching the Mars Perseverance Rover to the Red Planet with the Mars 2020 Mission. The rover is loaded with equipment to search for signs that there once was life on Mars. One device, called the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument, will be used to detect chemicals on the Martian surface that are linked to the existence of life. To keep the instrument working well, a team from the Astromaterials Research and Exploration Science (ARES) division at NASA's Johnson Space Center (JSC) recently built a new calibration device for the rover to check SHERLOC's function and properly tune it during the upcoming mission. "SHERLOC is pretty complicated, and we came up with a list of 11 things that all have to be calibrated on this instrument," said Marc Fries, ARES planetary scientist and Mars 2020 Perseverance Rover instrument co-investigator. "This sophisticated calibration device is also going to be used for a lot of other scientific and engineering investigations, and we're really excited that it's JSC's contribution to the Mars 2020 rover." SHERLOC is mounted on the end of the rover's seven-foot robotic arm and includes a laser, camera and chemical analyzers, called spectrometers. The sensitive components will be used together to search for substances that have been altered by water and possibly reveal evidence of past microscopic life on Mars.

"The rover's scientific instruments go through all sorts of harsh conditions from the time they leave the lab until they arrive on the surface of Mars. SHERLOC needed a way to make sure it still operates as expected once it's on the surface and throughout the duration of the mission," said Trevor Graff, a scientist from Jacobs who works for ARES.

The solution was to create the calibration target, or "cal target" for short. The device is approximately the size of a large cell phone and mounted on the front of the rover. On its face are 10 "targets," which consist of samples of different materials. The idea is that researchers will occasionally check SHERLOC's function by directing it to scan the different materials on the cal target. The researchers will already know what the readings on those materials should be when SHERLOC is working correctly. If the actual readings are off, they'll make adjustments to SHERLOC to get it set properly, or know to compensate for the errors when they analyze the data later.

Graff led the JSC cal target team, which included Jacobs engineers Ryan Weiner and Vinh Tran.

"I don't always get to see the hardware that I work on in person," Weiner said, "So I really enjoyed being so hands-on helping to assemble the calibration target."

"It was a great experience overall, and I'm confident the design will arrive on Mars in one solid piece," Tran added.


Science on the Side

In addition to tuning SHERLOC, the targets on the calibration device are serving double duty in other tests and experiments. For example, a number of the targets hold spacesuit materials that could one day be used to protect astronauts exploring Mars. SHERLOC's scans of those materials will not only help tune the instrument, but measure how the advanced fabrics and other suit materials will hold up in the Martian environment, too.

"We also plan to build a small Mars exposure instrument here at JSC, and match the conditions inside it with weather data from the rover," Fries said. "We'll then place an identical set of spacesuit samples inside the chamber and periodically remove them to, for example, test the strength of fabrics or the clarity of helmet visor plastics. The result is we'll be able to test spacesuit materials in Mars-like conditions long before astronauts ever go there."

Another target contains an actual sample of a meteorite ejected from Mars long ago and discovered on Earth in 1999. Researchers plan to closely watch the rock sample to see how the Martian environment alters it over time, which will help them understand the chemical interactions between the planet's surface and its atmosphere.

First Arab mission to Mars designed to inspire youth

The first Arab space mission to Mars, armed with probes to study the Red Planet's atmosphere, is designed to inspire the region's youth and pave the way for scientific breakthroughs, officials said Tuesday. The unmanned probe Al-Amal -- Hope in Arabic -- is to blast off from a Japanese space centre on July 15, with preparations now in their final stages. The project is the next giant step for the United Arab Emirates, whose colossal skyscrapers and mega-projects have put it on the world map. The UAE sent its first astronaut into space last year and is also planning to build a "Science City" to replicate conditions on Mars, where it hopes to build a human settlement by 2117. Omran Sharaf, the mission's project manager, said that apart from the ambitious scientific goals, the mission was designed to hark back to the region's golden age of cultural and scientific achievements. "The UAE wanted to send a strong message to the Arab youth and to remind them of the past, that we used to be generators of knowledge," he told AFP. "People of different backgrounds and religion coexisted and shared a similar identity," he said of the Arab world, where many countries are today wracked by sectarian conflicts and economic crises. "Put your differences aside, focus on building the region, you have a rich history and you can do much more."

- Narrow window -

Sarah al-Amiri, the mission's deputy project manager, said it was imperative that the project have a long-term scientific impact.

"It is not a short-lived mission, but rather one that continues throughout the years and produces valuable scientific findings -- be it by researchers in the UAE or globally," she told AFP.

She said that the probe will provide a comprehensive image of the weather dynamics in Mars' atmosphere with the use of three scientific instruments.

The first is an infrared spectrometer to measure the planet's lower atmosphere and analyse the temperature structure.

The second, a high-resolution imager that will provide information about the ozone; and a third, an ultraviolet spectrometer to measure oxygen and hydrogen levels from a distance of up to 43,000 kilometres from the surface.

The three tools will allow researchers to observe the Red Planet "at all times of the day and observe all of Mars during those different times", Amiri said.

"Something we want to better understand, and that's important for planetary dynamics overall, is the reasons for the loss of the atmosphere and if the weather system on Mars actually has an impact on loss of hydrogen and oxygen," she said, referring to the two components that make up water.

Sharaf said that fuelling of the probe is to begin next week.

It is scheduled to launch on July 15 from Japan's Tanegashima Space Centre and return to Earth in February 2021, depending on many variables including the weather.

"If we miss the launch opportunity, which is between mid-July and early August, then we'd have to wait for two years for another window," Sharaf said.

But hopes are high that the mission will take place as scheduled, and not be derailed by the coronavirus pandemic.

In a new sign of warming ties between Israel and Gulf Arab nations, the Jewish state Tuesday wished the UAE success with the mission.

We "hope this step will contribute towards deeper cooperation between all countries in the region," its foreign ministry's "Israel in the Gulf" Twitter account wrote in Arabic.

NASA's Perseverance Mars rover gets its wheels and air brakes

Final assembly and testing of NASA's Perseverance rover continues at Kennedy Space Center in Florida as the July launch window approaches. In some of the last steps required prior to stacking the spacecraft components in the configuration they'll be in atop the Atlas V rocket, the rover's wheels and parachute have been installed. Perseverance received its six flight wheels on March 30, 2020. While the rover took a test drive last December, it was on "flight spares" that wouldn't be making the trip to Mars. Designed for the kind of off-roading Perseverance will perform on the Red Planet, the wheels are re-engineered versions of the ones NASA's Curiosity has been using on its traverses of Mount Sharp. Machined out of a block of flight-grade aluminum and equipped with titanium spokes, each wheel is slightly larger in diameter and narrower than Curiosity's, with skins that are almost a millimeter thicker. They also feature new treads, or grousers: In place of Curiosity's 24 chevron-pattern treads are 48 gently curved ones. Extensive testing in the Mars Yard at NASA's Jet Propulsion Laboratory, which built the rover and manages operations, has shown these treads better withstand the pressure from sharp rocks and grip just as well or better than Curiosity's when driving on sand.

The Parachute
The job of adding Perseverance's parachute to the back shell, where the rover will be stowed on the journey to the Red Planet, took several days and was finished on March 26. Tasked with slowing the heaviest payload in the history of Mars exploration from Mach 1.7 to about 200 mph (320 kph) during the rover's landing on Feb., 18, 2021, the 194 pounds (88 kilograms) of nylon, Technora and Kevlar fibers are packed so tightly into a 20-inch-wide (50-centimeter-wide) aluminum cylinder that it is as dense as oak wood. When deployed at about 7 miles (11 kilometers) above the Martian surface, the chute will take about a half-second to fully inflate its 70.5-foot-wide (21.5-meter-wide) canopy.

The Perseverance rover is a robotic scientist weighing 2,260 pounds (1,025 kilograms). It will search for signs of past microbial life, characterize the planet's climate and geology, collect samples for future return to Earth, and pave the way for human exploration of the Red Planet. No matter what day Perseverance launches during its July 17-Aug. 5 launch period, it will land on Mars' Jezero Crater on Feb. 18, 2021.

Europe prepares for Mars courier

The first round-trip to the Red Planet will see a European orbiter bringing martian samples back to Earth. ESA is opening the door to industry to build the spacecraft that will deliver the precious rocks, dust and gas from Mars - the key to understanding whether life ever existed on our closest planetary neighbour. This 'take-away' service is called the Earth Return Orbiter, and will be ESA's major contribution to the Mars Sample Return campaign. The ESA Orbiter will carry NASA's Capture and Containment and Return System, which will rely on the ESA-led spacecraft for transit to and from Mars. Three launches from Earth and one from Mars - the first ever from another planet -, two rovers and an autonomous capture in Mars orbit are all part of an ambitious series of missions that ESA is embarking on together with NASA. The campaign aims to bring at least 500 grams of samples back from the Jezero crater that once held a lake and contains an ancient preserved river delta. The rocks in the area preserve information about Mars' diverse geology. NASA's Mars 2020 rover that is slated for launch in July 2020 will scientifically select the best samples to store in tubes and deposit them onto the martian surface for later retrieval. ESA is also studying concepts for a small 'fetch' rover to scurry quickly across the martian surface to locate and recover the stored samples. It would then carry them back to a football-sized canister that would be launched with a NASA Mars Ascent System - a small rocket.

Bringing samples from Mars is the logical next step for robotic exploration and it will require multiple missions that will be more challenging and more advanced than any robotic missions before. Accomplishments in robotic exploration in recent years have increased confidence in success - multiple launches will be necessary to deliver samples from Mars.

ESA is working with NASA to explore mission concepts for an international Mars Sample Return campaign between 2020 and 2030.

Three launches will be necessary to accomplish landing, collecting, storing and finding samples and delivering them to Earth.

NASA's Mars 2020 mission will explore the surface and rigorously document and store a set of samples in canisters in strategic areas to be retrieved later for flight to Earth.

Two subsequent missions are foreseen to achieve this next step.

A NASA launch will send the Sample Retrieval Lander mission to land a platform near the Mars 2020 site. From here, a small ESA rover - the Sample Fetch Rover - will head out to retrieve the cached samples.

Once it has collected them in what can be likened to an interplanetary treasure hunt, it will return to the lander platform and load them into a single large canister on the Mars Ascent Vehicle (MAV). This vehicle will perform the first liftoff from Mars and carry the container into Mars orbit.

ESA's Earth Return Orbiter will be the next mission, timed to capture the basketball-size sample container orbiting Mars. The samples will be sealed in a biocontainment system to prevent contaminating Earth with unsterilised material before being moved into an Earth entry capsule.

The spacecraft will then return to Earth, where it will release the entry capsule for the samples to end up in a specialised handling facility.

ESA and NASA are exploring the concepts for these missions, with ESA assessing the Sample Fetch Rover and Earth Return Orbiter. These will provide input to ESA's 2019 council at ministerial level, where approval will be sought for the missions. Mars Sample Return overview infographic.

The Earth Return Orbiter will capture the canister in orbit and transfer it safely to Earth, a return trip that will take about 13 months.

"We will have the responsibility of finding, capturing and transporting these precious martian treasures home for careful analysis in state-of-the-art labs on our planet," explains Sanjay Vijendran, ESA's Mars Sample Return campaign coordinator. "It's an interplanetary treasure hunt!"

Bringing Mars back to Earth

The Earth Return Orbiter is set to get onto the launch pad by 2026 from Europe's spaceport in Kourou, French Guiana. Through this call, ESA will be selecting a prime contractor for the spacecraft.

"The mission is becoming a reality, and we are proud to give European industry the chance to join the challenge," says Orson Sutherland, study manager for the Earth Return Orbiter.

The main challenges are the electric propulsion and power generation. "Not to forget finding and navigating the spacecraft to rendezvous with the football sized orbiting sample over 50 million km away from ground control," adds Orson.

The spacecraft will use technological heritage from ESA's most recently launched science mission, BepiColombo: both use electric propulsion and multi-stage detachable modules.

"Europe is ready to do its bit for the Mars Sample Return campaign, in close partnership with NASA, and is up to the challenge of putting the spacecraft onto the launch pad in 2026," says Orson.

Scientists find likely source of methane on Mars

The mystery of methane on Mars may finally be solved as scientists Monday confirmed the presence of the life-indicating gas on the Red Planet as well as where it might have come from. In the 15 years since a European probe reported traces of the gas in the Martian atmosphere, debate has raged over the accuracy of the readings showing methane, which on Earth is produced by simple lifeforms. Because methane gas dissipates relatively quickly -- within around 12 years on Earth -- and due to the difficulty of observing Mars' atmosphere, many scientists questioned previous studies that relied on a single data set. Now an international team of experts have compared observations from two separate spacecraft, taken just one day apart in 2013, to find independent proof of methane on our neighbouring planet. Furthermore, they conducted two parallel experiments to determine the most likely source of methane on Mars to be an ice sheet east of Gale Crater -- itself long assumed to be a dried up lake. "This is very exciting and largely unexpected," Marco Giuranna, from Rome's National Astrophysics Institute, told AFP. "Two completely independent lines of investigation pointed to the same general area of the most likely source for the methane." Europe's Mars Express probe measured 15.5 parts per billion in the atmosphere above the Gale Crater on June 16, 2013. The presence of methane in the vicinity was confirmed by readings taken 24 hours earlier by NASA's Curiosity rover. Using the data, Giuranna and the team divided the region around the crater into grids of 250 by 250 square kilometres.

One study then ran a million computer-modelled emissions scenarios for each section while another team studied images of the planet surface for features associated on Earth with the release of methane.

- 'Indicator of life' -

The most likely source was a sheet of frozen methane beneath a rock formation, which the team believes periodically ejects the gas into the atmosphere.

Giuranna said that while methane is a sign of life on Earth, its presence on Mars doesn't necessarily constitute evidence of something similar on the Red Planet.

"Methane is important because it could be an indicator of microbial life," he said. "But life is not required to explain these detections because methane can be produced by abiotic processes."

"Though not a direct biosignature of life, methane can add to the habitability of martian settings, as certain types of microbes can use methane as a source of carbon and energy," he added.

Though there is no liquid water on Mars, the European Space Agency said in February its imaging equipment had shown further evidence of dried up river beds, suggesting the Red Planet may once have been home to simple organisms.

Giuranna said that further research was needed to determine the extent of the methane ice sheet near Gale Crater.

If founded to be extensive, the methane it contains "could support a sustained human presence" on Mars as a possible source of fuel for industrial processes and a propellant for returning manned missions to Earth, he said.

Shaping the surface of Mars with water, wind and ice

ESA's Mars Express has imaged an intriguing part of the Red Planet's surface: a rocky, fragmented, furrowed escarpment lying at the boundary of the northern and southern hemisphere. This region is an impressive example of past activity on the planet and shows signs of where flowing wind, water and ice once moved material from place to place, carving out distinctive patterns and landforms as it did so. Mars is a planet of two halves. In places, the northern hemisphere of the planet sits a full few kilometres lower than the southern; this clear topographic split is known as the martian dichotomy, and is an especially distinctive feature on the Red Planet's surface. Northern Mars also displays large areas of smooth land, whereas the planet's southern regions are heavily pockmarked and scattered with craters. This is thought to be the result of past volcanic activity, which has resurfaced parts of Mars to create smooth plains in the north - and left other regions ancient and untouched. The star of this Mars Express image, a furrowed, rock-filled escarpment known as Nili Fossae, sits at the boundary of this north-south divide. This region is filled with rocky valleys, small hills, and clusters of flat-topped landforms (known as mesas in geological terms), with some chunks of crustal rock appearing to be depressed down into the surface creating a number of ditch-like features known as graben.

As with much of the surrounding environment, and despite Mars' reputation as a dry, arid world today, water is believed to have played a key role in sculpting Nili Fossae via ongoing erosion. In addition to visual cues, signs of past interaction with water have been spotted in the western (upper) part of this image - instruments such as Mars Express' OMEGA spectrometer have spotted clay minerals here, which are key indicators that water was once present.

The elevation of Nili Fossae and surroundings, shown in the topographic view above, is somewhat varied; regions to the left and lower left (south) sit higher than those to the other side of the frame (north), illustrating the aforementioned dichotomy. This higher-altitude terrain appears to consist mostly of rocky plateaus, while lower terrain comprises smaller rocks, mesas, hills, and more, with the two sections roughly separated by erosion channels and valleys.

This split is thought to be the result of material moving around on Mars hundreds of millions of years ago. Similar to glaciers on Earth, flows of water and ice cut through the martian terrain and slowly sculpted and eroded it over time, also carrying material along with them. In the case of Nili Fossae, this was carried from higher areas to lower ones, with chunks of resistant rock and hardy material remaining largely intact but shifting downslope to form the mesas and landforms seen today.

The shapes and structures scattered throughout this image are thought to have been shaped over time by flows of not only water and ice, but also wind. Examples can be seen in this image in patches of the surface that appear to be notably dark against the ochre background, as if smudged with charcoal or ink.

These are areas of darker volcanic sand, which have been transported and deposited by present-day martian winds. Wind moves sand and dust around often on Mars' surface, creating rippling dune fields across the planet and forming multi-coloured, patchy terrain like Nili Fossae.

The data comprising this image were gathered by Mars Express' High Resolution Stereo Camera (HRSC) on 26 February 2018.

ESA's Mars Express was launched in 2003. As well as producing striking views of the martian surface such as this, the mission has shed light on many of the planet's biggest mysteries - and helped to build the picture of Mars as a planet that was once warmer, wetter and potentially habitable. Read more about the past 15 years of Mars Express, and what the mission has discovered so far, here.

Mars Express Detects Liquid Water Hidden Under Planet's South Pole

Evidence for the Red Planet's watery past is prevalent across its surface in the form of vast dried-out river valley networks and gigantic outflow channels clearly imaged by orbiting spacecraft. Orbiters, together with landers and rovers exploring the Martian surface, also discovered minerals that can only form in the presence of liquid water. But the climate has changed significantly over the course of the planet's 4.6-billion-year history and liquid water cannot exist on the surface today, so scientists are looking underground. Early results from the 15-year-old Mars Express spacecraft already found that water ice exists at the planet's poles and is also buried in layers interspersed with dust. The presence of liquid water at the base of the polar ice caps has long been suspected; after all, from studies on Earth, it is well known that the melting point of water decreases under the pressure of an overlying glacier. Moreover, the presence of salts on Mars could further reduce the melting point of water and keep the water liquid even at below-freezing temperatures. But until now evidence from the Mars Advanced Radar for Subsurface and Ionosphere Sounding instrument, MARSIS, the first radar sounder ever to orbit another planet, remained inconclusive. It has taken the persistence of scientists working with this subsurface-probing instrument to develop new techniques in order to collect as much high-resolution data as possible to confirm their exciting conclusion.

Ground-penetrating radar uses the method of sending radar pulses towards the surface and timing how long it takes for them to be reflected back to the spacecraft, and with what strength. The properties of the material that lies between influences the returned signal, which can be used to map the subsurface topography.

The radar investigation shows that south polar region of Mars is made of many layers of ice and dust down to a depth of about 1.5 km in the 200-km-wide area analyzed in this study. A particularly bright radar reflection underneath the layered deposits is identified within a 20-km-wide zone.

Analyzing the properties of the reflected radar signals and considering the composition of the layered deposits and expected temperature profile below the surface, the scientists interpret the bright feature as an interface between the ice and a stable body of liquid water, which could be laden with salty, saturated sediments. For MARSIS to be able to detect such a patch of water, it would need to be at least several tens of centimeters thick.

"This subsurface anomaly on Mars has radar properties matching water or water-rich sediments," says Roberto Orosei, principal investigator of the MARSIS experiment and lead author of the paper published in the journal Science.

"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."

"We'd seen hints of interesting subsurface features for years but we couldn't reproduce the result from orbit to orbit, because the sampling rates and resolution of our data was previously too low," adds Andrea Cicchetti, MARSIS operations manager and a co-author on the new paper.

"We had to come up with a new operating mode to bypass some onboard processing and trigger a higher sampling rate and thus improve the resolution of the footprint of our dataset: now we see things that simply were not possible before."

The finding is somewhat reminiscent of Lake Vostok, discovered some 4 km below the ice in Antarctica on Earth. Some forms of microbial life are known to thrive in Earth's subglacial environments, but could underground pockets of salty, sediment-rich liquid water on Mars also provide a suitable habitat, either now or in the past? Whether life has ever existed on Mars remains an open question, and is one that Mars missions, including the current European-Russian ExoMars orbiter and future rover, will continue to explore.

"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," says Dmitri Titov, ESA's 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."

Mars Express launched 2 June 2003 and celebrates 15 years in orbit on 25 December this year.