Is there really water on Mars?

Since life as we know it -- even the most bizarre varieties -- depends on liquid water, scientists assume that it would also be a necessity for extraterrestrial organisms. Mars is replete with water, but most (if not all) of it is in frozen or vapor form. For instance, ice caps the planet's poles, and patches of ice lie over dunes in craters [source: Fountain].

But until the Mars Reconnaissance Orbiter started circling the planet and the Phoenix Mars Lander landed on it, most people assumed that if Mars once had liquid water, it hadn't for some time. The planet's atmosphere and temperature make the idea of liquid water seem impossible. The planet is extremely dry, and its distance from the sun keeps the temperature between 22 and -124 degrees Fahrenheit (-5.5 and -86.7 degrees Celsius).

However, liquid water on Mars wouldn't necessarily be the same as liquid water on Earth. If the water were highly acidic, for example, it would have a lower freezing point and could maintain its liquid state in the chilly climate [source: Lovett].

­But where would liquid Martian water come from? What else could have caused the depository streaks?

­While the sudden appearance of depository streaks thrilled many scientists, others began to question the flash-flood theory. Further analysis of at least one of the gullies suggested that its shape didn't match the way fast-moving water flows. The deposits' fingerlike shape suggested something granular and dry, like fine-grained sand, rushed through the valley [source: Lovett].

However, the shape of the gullies doesn't completely discount the possibility that there was liquid water involved. Even if the gullies were carved by sand, wet conditions could have initiated the landslide or a­ small amount of water could have mixed with dirt and sand to form slurry [source: Lovett].

The images that first got scientists speculating came from the High Resolution Imaging Science Experiment (HiRISE), a camera that can capture minute landscape details and geologic structures. It's one of six instruments that make up the Mars Reconnaissance Orbiter, which was launched with the mission to hunt for evidence of water. Scientists hope the mission will also clarify the climate and geology of the planet, but the orbiter's scientific payload focuses squarely on H₂­0.

By now, you've probably gathered that the orbiter isn't looking for some stray puddles or some body of water that scientists missed on previous surveys of the planet. Instead, the orbiter's cameras and spectrometers are searching for mineral deposits left by water. A sounder uses radar to find underground liquid reserves. Other cameras monitor clouds and dust storms. All the information from the Mars Reconnaissance Orbiter is relayed back to Earth through X-band and Ka-band radio waves that are picked up by the Deep Space Network antenna in Canberra, Australia.

­In the past, orbiting spacecraft have observed two groups of hydrated minerals on Mars: phyllosilicates, which formed 3.5 billion years ago when Martian water encountered rock, and hydrated sulfates, which formed 3 billion years ago due to evaporation. In 2008, however, the Mars Reconnaissance Orbiter discovered new hydrated minerals on the red planet in the form of hydrated silica, also known as opal. These newly discovered minerals formed when water was exposed to areas affected by meteorites or volcanic activity. These findings have shaved a billion years off previous estimates, indicating that Mars may have had liquid water as recent­ly as 2 billion years ago.

The orbiter also returned evidence of clay mineral deposits that only could have formed due to rock-fracture plumbing and water altering the landscape in early Martian history. Scientists think that flowing Martian groundwater formed these crevices in the planet's distant past.

­The Mars Reconnaissance Orbiter wasn't the only spy on the red planet over the last year. While the orbiter examined Mars from space, the Phoenix Mars Lander entered the planet's atmosphere to scope out conditions on the ground.

In May of 2008, the planet Mars received a rare visit from Earth. The Phoenix Mars Lander touched down in the previously unexplored far north to study Martian water. Such information could help scientists back home better judge if the planet could support life as we know it. After all, in the event of a manned mission to Mars, the presence of usable water could mean astronauts would have one less item to lug with them on their interplanetary trek.

­The lan­ding site was a prime area for exploration, since the northern polar region has plenty of water ice just beneath a very dry layer of soil. The Phoenix used its robotic arm to dig into the ground and collect samples of soil and ice, which were then analyzed for content. If that sounds like a piece of cake, bear in mind that it took earthbound scientists two full days just to successfully deploy the arm and prepare it for digging.

Despite the time and effort involved in every movement of the lander's limb, the Phoenix proved successful. It confirmed the presence of ice in the soil, glimpsed snow in the Martian sky and found evidence of both clay and calcium carbonate. This last discovery is particularly noteworthy since most clays and carbonates on Earth only form in the presence of liquid water.

The lander also discovered evidence of organic salts called perchlorates. Some experts argue that this last discovery kills the notion of life on Mars, as these salts rapidly decompose organic compounds. Still others hold out hope, pointing to some Earth species of bacteria that actually break down perchlorate. Might life on Mars have been similar to these bacteria?

That isn't the only new question scientists can look forward to tackling in future missions. The Phoenix also shed light on the red planet's humidity by using a spiky thermal and conductivity probe to detect rising and falling levels of water vapor in the air. Perplexingly enough, none of this moisture seems to collect on or in the thoroughly dry soil.

Originally scheduled for a three-month mission on the Martian surface, NASA renewed its mission twice, and, even as cold October temperatures forced the scientists to begin shutting down the lander's systems, it was still sending readings back to Earth. While wintering on Mars most likely means frozen entombment in solid carbon dioxide, NASA hopes to revive the robotic lander when temperatures increase enough to allow all its systems to operate again and its solar panels to collect energy.

The next mission to Mars was slated for a 2013 launch, when MAVEN, the Mars Atmosphere and Volatile Evolution spacecraft, made its way to the red planet to study what might have happened to its atmosphere. Scientists hoped MAVEN would shed more light on Mars' wet past and if life in any form has ever existed on the planet. But what did they find?

As our understanding of the enigmatic Martian landscape deepens, another key player entered the scene - the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft. Launched by NASA in November 2013, MAVEN embarked on a mission to unravel the secrets of Mars' ancient atmosphere, volatile history, and the tantalizing possibility of water on the Red Planet. While the Mars Reconnaissance Orbiter and Phoenix Mars Lander made significant contributions to our knowledge, MAVEN's focus on atmospheric processes and interactions has shed new light on the presence of water on Mars.

The primary goal of MAVEN was to decipher how Mars lost its thick atmosphere and, consequently, its liquid water over the course of billions of years. Researchers hypothesized that the planet's thin, tenuous atmosphere might have allowed water to escape into space. This loss could have transformed Mars from a once-watery world to the arid desert we observe today. Over the course of its mission, MAVEN meticulously studied the interactions between the solar wind and Mars' upper atmosphere, providing valuable insights into the processes responsible for the planet's atmospheric erosion.

Intriguingly, MAVEN's findings indirectly supported the existence of water on Mars. The spacecraft's observations revealed that certain atmospheric escape mechanisms could have led to the loss of hydrogen and oxygen, crucial components of water molecules. While MAVEN wasn't designed to directly detect water ice on the Martian surface, its revelations hinted at the possibility that water, locked away in ancient times, might still be hidden beneath the Martian surface as ground ice or within ice deposits. The discovery of features like ice sheets, ice-capped polar regions, and even seasonal changes such as the appearance of dark streaks hinted at the dynamic presence of water in various forms. These insights deepened our understanding of the planet's hydrological history and fueled the ongoing quest to unveil the extent of water on Mars.

NASA's MAVEN spacecraft continues its dedicated orbit around Mars, tirelessly examining the intricate structure and composition of the planet's upper atmosphere. In a testament to its versatility and ingenuity, MAVEN's role expanded in early 2019 when it transitioned to a lower orbit, assuming the vital role of a data-relay satellite for NASA's Mars 2020 rover. Originally planned for a two-year mission, MAVEN's remarkable fuel efficiency and endurance have defied expectations, allowing it to persist as an invaluable asset in our quest to comprehend the Red Planet's mysteries. With its mission extended well into the future, MAVEN stands as a beacon of scientific resilience, poised to continue unraveling the captivating secrets of Mars until at least 2030.

The question of whether there is water on Mars has captivated scientists and space enthusiasts alike for decades. Over the years, a wealth of evidence has gradually accumulated, painting a complex picture of the Martian water story.

So, is there water on Mars? Absolutely! While Martian H2O may differ from Earth's, it holds vital clues about the planet's ancient history and could prove invaluable for future exploration endeavors. Surprisingly, some of this water is trapped within rocks.