Mars Express Archives

November 27, 2022November 27, 2022 by Andy Tomaswick

Many Clouds on Mars are Driven by Dust, not Water

One of the benefits of having a cluster of satellites orbiting another planet is that scientists can then analyze that planet’s weather. Sometimes in that process, they find patterns that are strikingly similar to those found on our home planet. That was the case recently when a group of scientists from ESA used data from Mars Express to analyze cloud formation on Mars. To no one’s surprise, dust seemed to be at the core of that formation. But the resultant clouds looked very much like those found here on Earth – in the tropics.

October 13, 2022October 13, 2022 by Nancy Atkinson

Mars Express Watched Deimos Pass in Front of Jupiter and its Moons

That’s no moon … wait … yes, it is, and more!

ESA’s Mars Express has captured an unusual and rare occultation, all from its vantage point in orbit of Mars. The spacecraft’s orbit brought it to the right place where it could witness the moment Mars’ small moon Deimos passed in front of Jupiter and its four largest moons. Scientists say that celestial alignments like these enable a more precise determination of the Martian moons’ orbits.

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October 4, 2022October 4, 2022 by Matt Williams

Underground Liquid Water Detected on Mars? Maybe not

This image from NASA’s Mars Reconnaissance Orbiter shows the edge of the Martian South Pole Layered Deposit. Credit: NASA/JPL-Caltech/University of Arizona

When planning crewed missions to Mars, the key phrase is “follow the water.” When astronauts set down on the Red Planet in the next decade, they will need access to water to meet their basic needs. Following the water is also crucial to our ongoing exploration of Mars and learning more about its past. While all of the water on the Martian surface exists as ice today (the majority locked away in the polar ice caps), it is now known that rivers, lakes, and an ocean covered much of the planet billions of years ago.

Determining where this water went is essential to learning how Mars underwent its historic transformation to become the dry and cold place it is today. Close to twenty years ago, the ESA’s Mars Express orbiter made a huge discovery when it detected what appeared to be a massive deposit of water ice beneath the southern polar region. However, recent findings by a team of researchers from Cornell University indicate that the radar reflections from the South Pole Layered Deposit (SPLD) may be the result of geological layering.

August 24, 2022August 24, 2022 by Matt Williams

Want to Live on Mars? Here's Where the Water is

Mineral map of Mars showing the presence of patches that formed in the presence of water. Credit: ESA

When crewed missions begin to travel to Mars for the first time, they will need to be as self-sufficient as possible. Even when Mars and Earth are at the closest points in their orbits to each other every 26 months (known as “Opposition“), it can take six to nine months for a spacecraft to travel there. This makes resupply missions painfully impractical and means astronauts must pack plenty of supplies for the journey. They will also need to grow some of their food and leverage local resources to meet their needs, a process known as In-Situ Resource Utilization (ISRU).

In particular, astronauts will need to know where to find water on the Red Planet, which is no small challenge. Luckily, the European Space Agency (ESA) has created a mineral map showing the locations of aqueous minerals (rocks that have been chemically altered by water). This map was created by the Mars Orbital Catalog of Aqueous Alteration Signatures (MOCAAS) project and took over ten years to complete. When it comes time to select landing sites for crewed missions to Mars (in the next decade and beyond), maps like this will come in mighty handy!

July 24, 2022July 24, 2022 by Carolyn Collins Petersen

The Deepest Known Canyon in the Solar System, Seen From Space

Solar system worlds beyond Earth have amazing surface features. Thanks to planetary science missions, we see images of canyons, craters, and cliffs across a variety of worlds. Someday, those places will give mountain climbers and hikers new challenges. In particular, Mars will be a favored destination. Future hikers and mountain climbers will be spoiled for choice, even if they must wear space suits to get their thrill on.

For example, there’s the Valles Marineris canyon region. It’s the largest known such feature in the solar system, many times larger than the Grand Canyon here on Earth. The European Space Agency’s Mars Express orbiter just returned breathtaking images of this rift canyon.

January 28, 2022January 28, 2022 by Evan Gough

The Scientific Debate Rages on: Is there Water Under Mars’ South Pole?

There’s no surface water on Mars now, but there was a long time ago. If you ask most people interested in Mars, what’s left of it is underground and probably frozen.

But some previous evidence shows there’s a lake of liquid water under the planet’s South Pole Layered Deposits (SPLD). Other evidence refutes it. So what’s going on?

Science, that’s what.

July 30, 2021July 30, 2021 by Ralph Crewe

Bad News. Those Underground Lakes on Mars? They’re Probably Just Frozen Clay

Context map: NASA/Viking; THEMIS background: NASA/JPL-Caltech/Arizona State University; MARSIS data: ESA/NASA/JPL/ASI/Univ. Rome; R. Orosei et al 2018

If you were planning an ice-fishing trip to the Martian south pole and its sub-surface lakes observed by radar in 2018, don’t pack your parka or ice auger just yet. In a research letter published earlier this month in Geophysical Research Letters by I.B. Smith et al., it seems that the Martian lakes may be nothing more smectite, that is, a kind of clay. Should the findings of the paper, titled A Solid Interpretation of Bright Radar Reflectors Under the Mars South Polar Ice (a solid title if you ask me), turn out to be correct, it would be a significant setback for those hoping to find life on the red planet. So why were these supposed lakes so critical for the search for life on Mars? How were they discovered in the first place? Why have our dreams of Martian ice-fishing turned to dust (or, more correctly, clay)?

July 6, 2021July 6, 2021 by Andy Tomaswick

Potentially More Subsurface Lakes Found on Mars

One of the hardest things to reconcile in science is when new data either complicates or refutes previously findings. It’s even more difficult when those findings were widely publicized and heralded around the community. But that is how science works – the theories must fit the data. So when a team from JPL analyzed data from Mars Express about the Martian South Pole, they realized the findings announced in 2018 about subsurface lakes on Mars might have been more fraught than they had originally thought.

July 4, 2021July 4, 2021 by Matt Williams

Unfortunately, There are Other Viable Explanations for the Subsurface Lakes on Mars

Mars’ south polar ice cap. Credit: ESA / DLR / FU Berlin /

Ever since 1971, when the Mariner 9 probe surveyed the surface of Mars, scientists have theorized that there might be subsurface ice beneath the southern polar ice cap on Mars. In 2004, the ESA’s Mars Express orbiter further confirmed this theory when its Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument detected what looked like water ice at a depth of 3.7 km (2.3 mi) beneath the surface.

These findings were very encouraging since they indicated that there could still be sources of liquid water on Mars where life could survive. Unfortunately, after reviewing the MARSIS data, a team of researchers led from Arizona State University (ASU) has proposed an alternative explanation. As they indicated in a recent study, the radar reflections could be the result of clays, metal-bearing minerals, or saline ice beneath the surface.

October 1, 2020October 1, 2020 by Matt Williams

Mars Express Finds Even More Ponds of Water Under the Ground on Mars

Radar data collected by ESA’s Mars Express point to a pond of liquid water buried under layers of ice and dust in the south polar region of Mars. Credit: ESA

Evidence of Mars’ watery past is written all over the surface of the planet. Between dried-up river valleys, outflow channels, and sedimentary deposits, it is clear that Mars was once a much different place. But until recently, the mystery of where this water went has remained unsolved. This changed in 2018 when data obtained by the ESA’s Mars Express probe indicated the existence of water beneath the south pole of the planet.

According to the Mars Express probe’s Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS), this body of water is in a 20 km (~12.5 mi) wide area about 1.5 km (~1 mi) beneath the surface. And now, further analysis of the data by a team led by the Roma Tre University has revealed the existence of three new ponds, the largest of which measures about 20 x 30 km (~12.5 x 18.5 mi) and is surrounded by many smaller ponds.