Geochemical calculations by researchers at Tokyo Institute of Technology to determine how the water content of Mars has changed over the past 4.5 billion years suggest as yet unidentified reservoirs of water on the planet.
A warmer more watery primordial Martian landscape more closely resembling Earth has long been suggested from geochemical and geological observations. However, as Hiroyuki Kurakawa and colleagues in Japan point out in their recent report “the timing, processes, and the amount of the water loss have been poorly constrained.”
Their latest studies using geochemical meteorite data to understand how the volume of water has changed on Mars over its history suggest there is more water present there now than has so far been observed.
Today Martian water is considered to exist chiefly as ice at the poles of the planet. However geological observations of rocks containing water laid sediments suggest that lakes and oceans once existed. Previous studies have focused on the volumes of lake-like geological structures to extrapolate how much water was previously present on Mars.
In contrast the researchers at Tokyo Institute of Technology and colleagues at Nagoya University and Kyushu University in Japan determined the water quantities over the course of the planet’s history from ratios of the isotopes deuterium and hydrogen (D/H) in ancient meteorites.
Deuterium and hydrogen exist in water at a standard ratio at equilibrium. However hydrogen is lighter and escapes more readily so that the changes in the D/H ratio over the course of time can be used to determine how much water has been lost.
They compared their results with previous geological estimates of the primordial water volume and found discrepancies in the figures that suggest the existence of as yet unidentified reservoirs of water on Mars at present.
They hypothesize that these may be in the form of mid-latitude ice mantles or underground reservoirs.
As hydrogen from water molecules escape oxygen is left behind. These latest results also suggest greater quantities of this oxygen than current models account for.