Life on Mars: could microbes have travelled to Earth?

NASA'S Mars Curiosity rover has discovered more evidence that there used to be water on the red planet and that it could once have supported life, raising the possibility that we are all Martians.
 
The latest findings were announced yesterday after analysis of dust drilled from sediments in the giant Gale crater, which contained clay minerals that could only have been formed in water. The rover also discovered traces of sulphur, nitrogen, hydrogen, oxygen, phosphorus and carbon. These are the elements found in almost all biological molecules on earth.
 
One scientist described the samples, which came from an area of the Gale crater called Yellowknife Bay, as "paydirt".
 
"A fundamental question for this mission is whether Mars could have supported a habitable environment. From what we know now, the answer is yes," said lead Nasa scientist Michael Meyer, according to The Times.
 
As for the quality of the water on the planet, John Grotzinger, another member of the team, announced: "If you had been around when this water was around, you would have been able to drink it."
 
The results also reveal oxidised and non-oxidised chemicals. "Converting one into the other can release energy, which could have formed the basis of an ancient Martian microbial metabolism," reports The Economist.
 
Curiosity's aim was to find out if Mars could ever have sustained life, says The Guardian. "The discovery of clays that formed in water, the neutral soil conditions, and a chemical energy source for microbes, suggests the scientists finally have an answer."

The scientists have "no plans to quit now", according to Fox News. "They want to keep searching for signs of complex organics and investigate other sites, to gain a better understanding of how the Gale crater area has changed over time."
 
But each discovery throws up more questions, and Space.com asks if we are all Martians. "The discovery that ancient Mars could have supported microbes raises the tantalising possibility that life may have evolved on the red planet before it took root on Earth," it states. "And if so, could Earth life trace its lineage back to Mars?"
 
If microbes did exist on the planet, it says, they may have been "able to survive an interplanetary journey after being blasted off their home world by an asteroid impact" - and could have ended up flourishing on our planet. ·