MARSIS – water on the Red Planet

The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument on Mars Express was crucial in the search for and discovery of signs of liquid water on Mars, including a suspected 20-by-30 km lake of salty water buried under 1.5 km of ice in the southern polar region.

Operated by the Istituto Nazionale di Astrofisica (INAF), Italy, and fully funded by the Italian Space Agency(ASI), MARSIS sends low-frequency radio waves down towards the planet using its 40-metre long antenna.

Most of these waves are reflected from the planet’s surface, but significant amounts travel through the crust and are reflected at boundaries between layers of different materials below the surface, including ice, soil, rock and water.

By examining the reflected signals, scientists can map the structure below the surface of the Red Planet to a depth of a few kilometres and study properties such as the thickness and composition of its polar ice caps and the properties of volcanic and sedimentary rock layers.

From Windows 98 to Mars 2022

“After decades of fruitful science and having gained a good understanding of Mars, we wanted to push the instrument’s performance beyond some of the limitations required back when the mission began,” says Andrea Cicchetti, MARSIS Deputy PI and Operation Manager at INAF, who led the development of the upgrade.

“We faced a number of challenges to improve the performance of MARSIS,” says Carlo Nenna, MARSIS on-board software engineer at Enginium, who is implementing the upgrade. “Not least because the MARSIS software was originally designed over 20 years ago, using a development environment based on Microsoft Windows 98!”

The new software was designed together by the INAF team and Carlo, and is now being implemented on Mars Express by ESA. It includes a series of upgrades that improve signal reception and on-board data processing to increase the amount and quality of science data sent to Earth.

“Previously, to study the most important features on Mars, and to study its moon Phobos at all, we relied on a complex technique that stored a lot of high-resolution data and filled up the instrument’s on-board memory very quickly,” says Andrea.

“By discarding data that we don’t need, the new software allows us to switch MARSIS on for five times as long and explore a much larger area with each pass.”

“There are many regions near the south pole on Mars in which we may have already seen signals indicating liquid water in lower-resolution data,” adds ESA Mars Express scientist Colin Wilson.

“The new software will help us more quickly and extensively study these regions in high resolution and confirm whether they are home to new sources of water on Mars. It really is like having a brand new instrument on board Mars Express almost 20 years after launch.”

The martian workhorse

Old enough to vote in many places on Earth, Mars Express continues to deliver amazing science while remaining one of ESA’s lowest-cost missions to fly.

“Mars Express and MARSIS are still very busy,” says James Godfrey, Mars Express spacecraft operations manager at ESA’s ESOC mission operations centre in Darmstadt, Germany. “The team did a great job designing the new software, maximising its impact while keeping the patches as small as possible, helping us continue to get the most out of this veteran spacecraft.”

Find out more about the other new scientific and operational activities Mars Express has recently enabled on the Mars Express blog.