On Monday, NASA announced that it has the best evidence yet of liquid water on Mars.
The news came during a press conference on Monday morning, held at NASA's headquarters in Washington, D.C.
"Mars is not the dry, arid planet that we thought of in the past," Jim Green, director of NASA's Planetary Science Division, said.
"Under certain circumstances, liquid water has been found on Mars," he continued.
Scientists believe that water is essential for life, so discovering water on another planet is a key step forward in potentially finding life on another planet.
The water has been found in recurring slope lineae (RSL), a seasonal occurrence on parts of Mars. These begin to appear in the spring and disappear late in the fall.
After the initial announcement, they said "we have been investigating these streaks ever since their discovery. The key evidence was missing until now, and that is their chemical identity."
NASA was able to use an instrument on NASA's Mars Reconnaissance Orbiter, a satellite orbiting Mars, to detect the chemical identity through a process called spectroscopy.
Spectroscopy is a process where light reflected off of an object is analyzed to determine what the object is comprised of, and in the case of the RSLs it was determined that they were made of salty water.
These RSLs are far from rivers and streams, but rather water that slowly moves down the slopes of mountains on Mars during the summer months.
Mars is similar to Earth where it has seasons as a result of rotating on a 25-degree axis, which is slightly greater than Earth's tilt.
Scientists believe that Mars once had plenty of water and a thick atmosphere that could have been comparable to present day Earth.
"If we go back 3 billion years, Mars was a very different planet," Green said.
Green added that there could have been a lake as big as a mile deep, but something happened and Mars suffered a major climate change that caused the water to disappear and the atmosphere to become thinner.
NASA has several missions planned for the Red Planet over the next several years, including a rover that is set to land on the Red Planet in 2020.
This rover will be similar to Curiosity, a rover currently on Mars, and will help pave the way for future human exploration.
One of the many things that NASA hopes to use this rover for is to test the ability to extract oxygen from the planet's carbon-dioxide atmosphere. This would be very useful for the future exploration of the Red Planet.