The Mars Express orbiter, a stalwart in the exploration of the Red Planet for the past two decades, has made a groundbreaking discovery that could reshape our understanding of Mars’ geology and climate. According to findings from the European Space Agency’s (ESA) Mars Express mission, enough water ice lies beneath Mars’ equator to form an ocean between 4.9 and 8.9 feet (1.5 and 2.7 meters) deep if melted – a revelation of colossal proportions.
This remarkable revelation comes as a result of extensive radar observations conducted by the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument aboard the Mars Express orbiter. The ice deposits were found buried beneath the equatorial region, within the Medusae Fossae Formation (MFF), a vast expanse characterized by wind-sculpted deposits measuring hundreds of kilometers across and several kilometers high.
Lead researcher Thomas Watters of the Smithsonian Institution expressed excitement, stating, “Excitingly, the radar signals match what we expect to see from layered ice and are similar to the signals we see from Mars’ polar caps, which we know to be very ice-rich.”
The ice-rich deposits, estimated to be up to 3000m thick, extend a staggering 3.7km (2.3 miles) underground and are capped by a layer of hardened ash and dry dust hundreds of meters thick. While the equatorial location is advantageous for potential future crewed missions, the depth at which the water-ice is buried presents a significant challenge for extraction.
The discovery builds upon earlier observations made by Mars Express over 15 years ago, which detected deposits beneath the Medusae Fossae Formation. The recent MARSIS observations dispel previous uncertainties about the composition of these deposits, indicating that they are indeed water ice rather than dust. The density and transparency of the deposits align with the characteristics expected of water ice, as opposed to a dense pile of dust.
The question of how such significant quantities of water ice ended up buried at Mars’ equator remains a topic of intrigue. Past missions, such as NASA’s Phoenix mission and Mars Express, have uncovered subsurface ice at various latitudes, offering tantalizing hints about Mars’ climatic evolution.
The presence of subsurface water-ice at low and equatorial latitudes suggests a vastly different climate in Mars’ distant past. Mars’ axial tilt, which has undergone chaotic variations over its history, may hold the key to understanding how water-ice formed at the equator during periods of high obliquity. This ice could have been subsequently buried by ash and dust falls, preserving it beneath the surface till the present day.
Colin Wilson, an ESA Project Scientist for Mars Express and the Trace Gas Orbiter, remarks, “This latest analysis challenges our understanding of the MFF and raises as many questions as answers. How long did these ice deposits form, and what was Mars like at the time?”
The implications of this discovery extend beyond Mars’ geological history, shedding light on the dynamic interplay between climate, water, and the planet’s ever-changing surface. The findings are detailed in a paper published in Geophysical Research Letters, marking a pivotal moment in our ongoing exploration of the mysteries hidden beneath the Martian surface.