Pictures of the planet Mars show a rocky, lifeless scene. It is hard to imagine plants or animals could ever exist there. But scientists continue to look for evidence.

NASA, America's space agency, has found evidence that, a long time ago, there was surface water on the Red Planet. Scientists believe water is necessary to support life as we know it. So since that discovery, they have been looking for chemicals that would be present if there once was -- or still is--- life on the planet.

At a December 13 conference in California, NASA scientists reported a breakthrough. They said for the first time that they had found very small amounts of an interesting element. It is called boron.

John Grotzinger is the lead scientist for Curiosity, the space vehicle on Mars that is exploring the planet.

"We have an instrument called the chemistry camera, which has made a detection of boron. And boron is interesting because in some scenarios for the origin of life, boron is able to help catalyze some of the reactions that build materials that could eventually become part of RNA molecules."

In other words, a camera on Mars showed the element boron. Boron is important because it could help build RNA molecules. And RNA molecules are important because they are one of the essential building blocks for life.

What's next?

One of the next steps in the scientists' search for life on Mars comes in 2020. That year, the next spacecraft is scheduled to launch. It will send rocks from Mars back to Earth.

Scientists in Britain are getting ready for those Mars rocks now. Using a powerful microscope, they have already examined 200-million-year-old volcanic rocks found deep in the Pacific Ocean.

The microscope revealed holes made by tiny living things called microbes. Microbes are the oldest form of life on Earth. They are only the size of one cell.

Peter Cumpson works with Newcastle University.

"What we've been able to do is to look in detail at the carbon chemistry within those tiny structures and identify that as being the remnants of some form of life, probably fungal related."

Next, the scientists in Britain will examine meteorites formed from ancient material from Mars. The material comes from a time when Mars would have been more likely to sustain life.

Graham Purvis explains what they will be looking for in the material. He is a geoscientist with Newcastle University.

"What we intend to do is have a look at some of the rocks that may be available from NASA, which date back to a time when Mars was much warmer and wetter, and have a look at some of the structures and chemical signatures that we see in those rocks."

The scientists hope to find tiny microbe holes in the ancient material similar to the ones they saw in the ocean rocks. If they do, they predict that the rocks coming directly from Mars will also show signs of life.

That, in turn, could finally prove that we are not alone.

I'm Anne Ball.

George Putic wrote this story for VOA News. Anne Ball adapted it for Learning English. Kelly Jean Kelly was the editor.