Perseverance finds Mars river could have been ‘wilder,’ Mars Express takes new volcano images

by Bella Richards

May has been a big month for scientific discoveries on Mars, as NASA’s Perseverance rover has continued to find more convincing evidence of what could have once been a “deeper and faster-moving” river than data initially suggested. New images taken by the rover’s main camera show two mosaics of course sediment grains and tall, curving layers of rock that suggest the river once flowed powerfully through the region.

But Perseverance isn’t alone in its discovery, as the European Space Agency’s (ESA) Mars Express orbiter has also had a busy month, as it studied the Martian planet’s second tallest volcano, and has captured new, stunning images of its fissured flank. These images provide a deeper glimpse of how the grooves on the surface were created, whether by water or lava.

Mars is the most explored planet in the Solar System (outside of Earth) due to its interesting landscape that could harbor signs of ancient microbial life. Perseverance landed on Mars in February 2021 and since then has been working with its helicopter companion, Ingenuity, to study its surface and cache samples of the Martian surface to return to Earth. Mars Express has been surveying the Red Planet since its launch in 2003 and continues to surpass what was expected to be only a two-year mission.

A wilder ancient river

Since its landing on Mars, Perseverance’s primary task has been to study and cache samples from Jezero Crater, a crater located to the west of a flat plain called Isidis Planitia. The crater was chosen as the spacecraft’s landing location as it is believed to have once been home to an ancient river delta.

The spacecraft has made several discoveries that suggest the former existence of an ancient river, but only now has it found that the water’s flow could have been much wilder than expected. Perseverance is currently exploring the top of a “fan-shaped pile” of 820-foot-tall sedimentary rock which was formed with curving layers. Scientists have been trying to figure out whether it once hosted shallow streams or a deeper, more powerful water system.

Martian rocks that may have been formed by a fast moving, wild river. (Credit: NASA/JPL-Caltech/ASU/MSSS)

With new images captured by the rover’s Mastcam-Z instrument, which is mounted on its mast and considered the ‘main eyes’ of the spacecraft, scientists have found that two new mosaics showing coarse sediment grains and cobbles suggest the former existence of “high-energy river”.

With this new glimpse, scientists are now trying to identify what kind of river this could have been (i.e. whether it’s like the Mississippi with a “snakelike” landscape or a “braided river” like Nebraska’s Platte). From Perseverance’s view, the curved layers have been arranged in rows that ripple out across the landscape, suggesting either remnants of sandbars that formed in the river, or riverbanks that have shifted over time.

“The more powerful the flow of water, the more easily it’s able to move larger pieces of material,” said Libby Ives, a postdoctoral researcher at NASA’s Jet Propulsion Laboratory (JPL).

These images were taken from the location of the ‘curvilinear unit’ within the Jezero Crater. The first mosaic features one part of the unit, called ‘Skrinkle Haven.’

The second mosaic, an isolated hill called ‘Pinestand’, shown in the new images and located about a quarter mile from Skrinkle Haven, depicts 66-foot-high sedimentary layers that point toward the sky. The scientists also believe that these unusually tall layers of rock were formed by a river but are seeking other explanations as well.

Perseverance’s view of Pinestand. (Credit: NASA/JPL-Caltech/ASU/MSSS)

“These layers are anomalously tall for rivers on Earth,” Ives continued. “But at the same time, the most common way to create these kinds of landforms would be a river.”

NASA’s Curiosity rover, another rover that has been studying Gale Crater on Mars since 2012, has found evidence of an ancient river much less powerful and shallow than what could have existed in Jezero.

More signs of water at Belva Crater

Adding to the already growing signs of water at Jezero Crater, Perseverance has taken 152 new images of a nearby crater that “indicate the presence of a large Martian sandbar.”

Belva Crater was likely created by the impact of a meteorite long ago and features 0.6 miles of exposed bedrock and sedimentary layers of rock that are angled downwards. The images, taken on April 22 and released on May 18, show “dipping beds” that could prove a sandbar made of sediment was deposited by a river channel flowing into the Jezero Crater lake.

Perseverance’s image of Belva Crater. (Credit: NASA/JPL-Caltech/ASU/MSSS)

“Mars rover missions usually end up exploring bedrock in small, flat exposures in the immediate workspace of the rover,” said Katie Stack Morgan, Perseverance’s deputy project scientist at JPL said. “That’s why our science team was so keen to image and study Belva. Impact craters can offer grand views and vertical cuts that provide important clues to the origin of these rocks with a perspective and at a scale that we don’t usually experience.”

Scientists studying the images are trying to figure out whether the large boulders were either formed by the meteorite impact or moved into the crater by the river system.

In a blog post from NASA posted on May 16, Perseverance recently performed an abrasion called “Ouzel Falls.” The image shows large grains created by the abrasion, and could be useful for “exploring elemental and mineral composition,” the blog post explains.

Mars Express captures Ascraeus Mons

ESA’s Mars Express orbiter arrived at Mars in December 2003 and was developed to study the planet’s atmosphere, surface, subsurface, and Mars’ moons Phobos and Deimos. Currently, the orbiter is exploring Martian volcanoes, and just imaged the pitted, fissured flank – the side of a volcano where lava can erupt from – of Ascraeus Mons.

The volcano is located in the Tharsis region of Mars and was discovered in 1971 by NASA’s Mariner 9 – the first spacecraft to ever orbit another planet, just ahead of the Soviet Union’s Mars 2. Ascraeus Mons is 18 kilometers high and is just shy of the tallest volcano on Mars – and in the entire Solar System – Olympus Mons, which is 25 kilometers high.

The image was captured by the orbiter’s High-Resolution Stereo Camera (HRSC), which can combine images at two different resolutions and provides 3D imaging to reveal the topography of Mars in color.

The flanks of Ascraeus Mons, as imaged by Mars Express. (Credit: ESA/DLR/FU Berlin)

Mars Express’ image shows many interesting discoveries of the lower southern flank of the volcano, as well as a 70-kilometer patch of collapsed terrain depicting lava flows and tubes, chains of craters, and large fissures.

To the right of the image is “wrinkled lava flows,” which meet chains of “pit craters” where strings of circular depressions have combined and coalesced to form troughs.

“These chains and troughs likely form where hidden voids lie below the surface, causing the ground to become unstable and collapse – a bit like a sinkhole,” ESA said. “The subsurface voids are thought to be created as the surface layer of a lava flow rapidly cools and hardens; the lava flow beneath then ceases and ebbs away over time, leaving tube-shaped pockets of space lurking several meters below ground.”

The surface to the left of the image shows the “sinuous rilles” — small, snaking channels without rims — which remain a mystery to scientists. ESA scientists are still unsure how these are formed but believe it may involve flows of lava, ash, water, or all of the three combined.

In the left part of the image, large fissures of up to 40 kilometers long are seen, with “braided channels” that branch out and create separate islands of Martian terrain. Again, ESA believes these are likely to have been formed by water, or even from melted ice build-up on the flanks of the volcano.

Mars continues to be one of the most interesting planets to explore, and activity will only ramp up in the future, with SpaceX’s Starship expected to transport humans to Mars. Scientists will also eventually get an even closer look at the Martian planet, as NASA and ESA unveiled updated architecture for their ambitious Mars Sample Return mission in July 2022, which will do, as the name suggests, return Mars samples that have been collected by Perseverance to Earth.

(Lead image: Perseverance takes a selfie after depositing one of its surface sample tubes onto the Martian surface. Credit: NASA/JPL-Caltech/MSSS)

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