After a recent discovery of hydrated mineral deposits on Mars’ surface, scientists like Robert Egler, a senior lecturer in physics, are almost sure water once flowed across the red planet’s surface.

The discovery also brings those who believe there may be life on Mars — at least at the microbial level — one step closer to knowing the answer.

“If we’re curious about the possibility of life in Mars, then knowing that it had water as liquid in its distant past is important,” Egler said. “Knowing that there was life on other planets would be a big deal. Not as big a deal as if they sent us a message, but knowing that they’re there would mean something.”

Water on Mars isn’t a new concept. It’s one almost as old as telescopic images of the planet, which indicate ice caps at its tip.

But the Mars Phoenix Lander, a robotic spacecraft, recently took a sample of Martian subsoil that contained phyllosilicate deposits. The mineral is one that, according to Guy Webster of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., contains water.

Scientists have guessed water once occupied the planet’s seemingly dry lake and stream beds.

“We’ve known there’s been a lot of water on Mars for a long time. We’ve seen polar ice caps and water vapor. Finding water frozen in subsoil is a big deal,” Egler said. “Most people would agree now that there was flowing water on Mars. From earlier spacecraft studies, most people would agree there was standing water.”

But the Martian atmosphere as it is now is too thin to sustain water. So if water did exist a few million years ago, the Martian atmosphere had to change.

“The atmosphere on Mars is not dense enough to allow water to stay as a liquid,” Egler said, comparing the atmosphere’s effect on water to what happens when solid carbon dioxide melts on Earth. “When the CO2 melts, it goes from being frozen to a gas. In Mars, water goes from being frozen to being a gas.”

The atmosphere’s chang over time could also bring to light the “processes on a planetary scale,” which Webster said can resemble “the processes on Earth.”

“It’s apparent from many things about Mars that it once had a denser atmosphere, it was warmer, and water could be more stable on the surface. It can’t do that with the atmosphere that’s there now,” he said. “Earth and Mars are very different, but some of the processes are comparable. It’s not like, ‘Oh, we see this process on another planet and that’s what’s going to happen on Earth.'”

The Mars Phoenix Lander reached its destination five months ago, and it was set to cease communication between the red planet and NASA three months afterward, according to a NASA press release. But with its last communication to Earth on Nov. 2, it lasted two extra months.

The lander was also the first robotic spacecraft to collect, sample and test Martian subsoil, Webster said. Previous rovers and satellites have given scientists a picture of what the terrain looks like, as well as sample loose soil, but have not dug below the surface.

“The Mars Phoenix Lander put some samples of ice mixed with soil into instruments on the deck of the lander and was able to verify, indeed, it was water,” Webster said. “The lander has seen frost, but to be able to touch it and taste it, the Phoenix Lander was the first to do that.”

Analysis from the on-site soil composition the lander performed, Webster said, found carbonate minerals that are “again an indicator that the mineral has been affected by water.”

And knowing the mineral exists on Mars, Egler said, has made most scientists believe water once flowed across the red planet. But he said for scientists to look for evidence of microbes — either ones that are alive or remnants what was once alive millions of years ago — the rover must send a sample back to Earth for tests.

No such mission is scheduled, Webster said.

“There are talks about how to design one and what it would take,” Webster said. “The next mission will send a rover capable of assessing whether Mars’ habitats are capable of sustaining life.”

Analysis of surface soil and subsoil samples help scientists decide where they should send the next rover — especially if it’s one that is going to send back a sample.

“We have to determine under what kinds of conditions is it favorable for preserving the evidence of life, if there was life,” Webster said, adding that NASA has plans to send a science lab to Mars sometime next year. The lab will conduct more soil samples to find a better place for the rover to land.

Egler said this step is important, since scientists cannot use one sample to determine whether there is life on Mars.

“We’ve found life on Earth in some places that are extremely inhospitable,” Egler said. Scientists have found life at the bottom of black, boiling-hot seas as well as imbedded thousands of feet within ice caps, he said.

“The next step is to send something up that can specifically dig into some ice a meter below the surface,” Egler said, “to see if there’s life there.”

The Mars Voyager, another robotic spacecraft, provided a rudimentary sample of the “first couple inches of the surface,” Egler said. This kind of sample would be able to determine whether there is or was life in a specific location of Mars, but it would not do much to predict whether the planet sustained life.

“It would be kind of like sending spacecraft to Earth, digging up some of the Sahara Desert and deciding there’s no life on Earth,” he said.

Scientists are on the right track with the Mars Phoenix Lander, Webster said. In collecting samples from different times, different places and different surface depths, scientists will be able to get a more general picture of Mars.

“What these samples add up to is that there’s sort of a diversity of types of environments that were wet. The conditions on Mars haven’t been uniform on the planet for a given time,” Webster said. “The soil that the Phoenix is analyzing is stuff that’s been laid down in relatively few millions of years.”

Previous missions have sampled younger soil, which might contain fewer water-bearing minerals.

“If we’re going to go send a mission to send out a sample and detect life on Mars, you wanna send it to the right place,” Webster said.