Astrophysics: the Marsis radar reveals that on Mars all that echoes is not ice
There would be no ice in the subsurface of Martian Meridiani Planum, based on data collected by the MARSIS radar on board the European Mars Express mission. This is the result of a new study published in the journal Geophysical Research Letters.
The study, “Radar sounder evidence of thick, porous sediments in Meridiani Planum and implications for ice-filled deposits on Mars”, suggests that the electrical properties of the Martian subsurface of the Meridiani Planum, an area on the planet’s equator explored by NASA’s Opportunity rover, can be misleading as to its composition. In fact, low dielectric constants measured on the surface are generally interpreted as indicators of the presence of ice.
Opportunity had already found that the Meridiani Planum area was rich in deposits of hematite, a mineral that formed, like on Earth, in standing water. However, the composition of the underlying layers was, until today, a mystery.
Thanks to the high resolution of the data acquired by the Marsis (Mars Advanced Radar for Subsurface and Ionospheric Sounding) radar, managed by the Italian Space Agency – ASI and which was reprogrammed for the occasion to obtain more accurate measurements, the scientists were able to develop a compaction model for the deposits of Meridiani Planum. This model indicates that the low dielectric constant of the Meridiani Planum deposits is consistent with a thick layer of ice-free, porous, basaltic sand. This study is fundamental to identify techniques that may help find the planet’s areas with accessible water ice.
The Marsis radar, developed on behalf of ASI by Sapienza University of Rome, in collaboration with the JPL and produced by Thales Alenia Space Italia, works by sending low frequency radio pulses that penetrate into the layers of the subsurface and are reflected back when they encounter a change in the density or composition of the materials. By analysing these echoes it is possible to determine the dielectric constant.
“Marsis”, said Angelo Olivieri, ASI’s coordinator for the Mars Express mission, “operating on the probe since 2005, the year when the antenna was deployed, is the first radar produced in Italy able to provide information on the composition of a planet’s subsurface layers and in all these years it has contributed significantly to our knowledge of the composition of Mars”.
“The Marsis radar on board the Mars Express spacecraft is a technologically advanced instrument with very high computational capabilities, which allow real time processing of the acquired signals”, said Andrea Cicchetti from the National Institute for Astrophysics – INAF in Rome and Operations Manager.
“To be able to collect high resolution data, it was necessary to reconfigure the instrument by operating surgically on the key parameters of the on board software”, said Andrea Cicchetti. Another advantage of this new configuration “is that it is possible to directly send back to Earth raw data, unprocessed by the on board software. This will allow a more extensive analysis of the data using the most appropriate and recent processing techniques”.