Martian Life’s Last Stand

If there was life on Mars, scientists may have found its final resting spot.

Scientists have found water-bearing deposits on Mars that are out of step with what was happening elsewhere on the planet, raising the prospect that the sites could have hosted Martian life's last stand.
The deposits are a type of clay called smectites, which contain a blend of silica with aluminum, iron or magnesium. They form in the presence of water.
The deposits were found in an unlikely locale -- roughly 30 feet up from the ground inside two troughs in Noctis Labyrinthus ("the labyrinth of the night"), a maze-like system of deep valleys located near the western end of the massive Valles Marineris canyon that cuts across the face of Mars.

Other smectites have been found on Mars, but only in areas with rock dating back to an older period in the planet's history, known as the Noachian age, which spans from about 3.6 billion to 4.5 billion years ago.
The planet's climate is then believed to have shifted, leading to a new geologic epoch marked by minerals that formed under more acidic conditions.
"Sofar, we've found these kinds of clays in the very oldest terrain," lead research Catherine Weitz, with the Planetary Science Institute, told Discovery News. "In our study, we see these same kind of smectites, but they formed in these depressions, these troughs, that are probably much younger."

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