Here is a bit more background on what might make the shift in search focus in regards to the red planet:

Considering Mars’ wet history, and its many similarities to Earth, scientists are actively seeking signs that life once existed there. The Red Planet may never have hosted plants or animals, but microscopic life-forms may have survived, even thrived, in that watery Martian environment 3 or 4 billion years ago.

Alfonso Davila is a research scientist at the SETI Institute and the NASA Ames Research Center, who studies how microbial life survives in the Atacama Desert — the closest natural analogue of modern Mars on Earth.

“There is an underlying assumption that if there was life [on Mars], it disappeared with the disappearance of water,” Davila said. “But this is not necessarily the case.”

Davila said the discussion in the scientific community about searching for life on Mars has been focused on hunting for fossils preserved in sediments that were likely formed in the presence of water. He is submitting a paper for publication that pushes for a second approach, which is looking for the life-forms that survived on the Martian surface when most or all of the liquid water had disappeared. Davila’s coauthor on the paper, Dirk Shulze-Makuch, a professor in the School of the Environment at Washington State University, presented the conclusions of the paper at the Astrobiology Science Conference in Chicago in June.

This does make sense potentially.  Why ignore what could be right in front of you and instead search for evidence of something from the past?

thanks to space.com for the great info