Hey, Space Fans! Every weekend here at Space.com, you may have noticed we highlight the latest episode of the podcast This Week In Space, a TWiT show co-hosted by yours truly and my friend and colleague Rod Pyle, a space historian and editor of the National Space Society magazine Ad Astra.
This Week In Space episodes usually drop each Saturday, but this week we're doing something a bit different. To mark the 50th anniversary of NASA's Viking landings (Viking 1 touched down on Mars on July 20, 1976), Rod and I will host a special live taping of the podcast to discuss all things Martian starting at 1:30 p.m. EDT (1730 GMT). It should last up to 90 minutes.
Joining us on the podcast will be:
Dr. Pascal Lee, a planetary scientist, geologist and artist with the SETI Institute, Mars Institute and NASA Ames Research Center.
Dr. Penny Boston, an astrobiologist and speleologist (the study of caves) with the New Mexico Institute of Mining and Technology.
During our discussion, we'll touch on the personal and scientific impacts of NASA's Viking Mars landings and look at where Mars exploration may go in the modern age. We might even discuss the best places for the hunt for signs of life: the surface or inside Martian caves?
So if you're a Mars fan or a casual space aficionado, join us today at 1:30 p.m. EDT to get a detailed look at NASA's Viking Mars landings and their lasting impact on Martian exploration.
The first-ever photo captured on the surface of Mars, snapped on July 20, 1976 by NASA's Viking 1 lander. (Image credit: NASA/JPL)
You're looking at history. What might seem like a simple black-and-white picture of some rocks is actually the first photograph ever taken on the surface of Mars.
What is it?
Bright and early on the morning of July 20, 1976, NASA's Viking 1 lander touched down on the surface of Mars. This moment 50 years ago marked the first fully successful touchdown on the Red Planet, and, pretty much as soon as it landed, Viking 1 captured the first image of the Martian surface.
The Soviet Union had already made multiple Mars landing attempts, all of them failures to some degree. The nation's Mars 3 lander did manage to survive its landing initially in December 1971, but it lost contact less than two minutes later.
Viking 1 did more than just survive. While its mission tasked the lander with studying the planet for 90 days after landing, it lasted over six years on the planet and made some incredible observations. The Viking 1 lander worked in tandem with an orbiter by the same name, and was soon joined at Mars by Viking 2, another lander/orbiter pair.
Why is it incredible?
It has now been 50 years since Viking 1's historic first, which opened our eyes to the Martian surface. And NASA has kept improving technologies and exploring further on Mars ever since. Agency rovers began scouring the planet's surface in the 1990s, so we have gathered data on the planet's surface for decades upon decades at this point.
But in 1976, no one had ever seen the surface of Mars close up. This view was preceded by science fiction like Ray Bradbury's "The Martian Chronicles," which painted fantastical possibilities about what it might really be like on Mars. With Viking 1's view, we finally got some concrete evidence of the reality on the planet.
In 50 years, our understanding of Mars, our solar system and beyond has grown tremendously. But with each major accomplishment, we can look back at previous milestones such as this to see the stepping stones that paved the way to get us there.
Swelling from a razor-thin crescent into a cratered world before fading back into the darkness, Mars gave NASA's Psyche spacecraft both a spectacular view — and a 1,000-mph boost toward its namesake asteroid.
A new time-lapse video released by NASA, stitched from images taken throughout May, captures the probe's month-long encounter with Mars. On May 15, Psyche swooped within 2,864 miles (4,609 kilometers) of the surface, using the planet's gravity to boost its speed and adjust its trajectory toward asteroid Psyche, a metal-rich world in the main asteroid belt between Mars and Jupiter that the spacecraft is scheduled to reach in 2029.
"This gravity assist was years in the making, and the navigation team nailed it — Psyche flew by Mars on exactly the trajectory we needed to set us on a path to rendezvous with the asteroid in the summer of 2029," Bob Mase, Psyche's project manager at NASA's Jet Propulsion Laboratory in California, said in a statement.
A screenshot from the timelapse, showing Psyche approaching a crescent Mars. (Image credit: NASA/JPL-Caltech/ASU/True Story Films)
Approaching from a steep or what scientists call a "high phase" angle relative to the sun, Psyche initially caught Mars as a slender crescent with just 4 percent of its disk illuminated and its thin atmosphere glowing in scattered sunlight, Hannah Zigo, a Psyche team member at the Arizona State University, said in a NASA video accompanying the statement.
As the spacecraft closed in, the video follows Mars steadily expanding to reveal numerous craters puncturing its surface, the ancient double-ringed Huygens crater and the south polar ice cap before receding in the spacecraft's rearview.
The flyby served a dual purpose. By aiming Psyche's suite of instruments at a well-studied world, engineers say they calibrated and validated the spacecraft's scientific payload ahead of its 2029 destination.
"We didn't anticipate big discoveries, given how extensively the planet has been studied," Lindy Elkins-Tanton, principal investigator for the Psyche mission at the University of California, Berkeley, said in the statement, "but we did complement Mars science with the data we collected through Psyche's unique perspective."
All three of the spacecraft's science instruments performed as expected, according to NASA. Its gamma-ray and neutron spectrometer, designed to determine the asteroid's elemental makeup, detected the predicted surge of escaping neutrons during closest approach, confirming its operational readiness.
The mission's magnetometer, which will search for evidence that asteroid Psyche is the metallic core of an early planetesimal, recorded its first magnetic signature from a planetary body since its launch in 2023, detecting the bow shock where the solar wind meets Mars' magnetic environment.
Psyche's twin multispectral cameras also passed their calibration tests, capturing the frames for the time-lapse while spotting Mars' tiny moons, Phobos and Deimos, from a distance, the NASA statement read.
Spotting the moons served as "a practice for the satellite search that we'll use at the asteroid Psyche to look for any moonlets there," Jim Bell, a planetary scientist at Arizona State University who leads the multispectral imager instrument team, said in the statement.
With Mars in its rearview and its instruments fully vetted, Psyche remains locked on course for its summer 2029 rendezvous with the metal asteroid.
"The spacecraft is in great shape, and we're on schedule to resume sustained thrusting with the solar-electric propulsion system later this fall," Mase said.
Half a century after first putting hardware down on Mars, NASA is looking to explore the Red Planet's skies.
On July 20, 1976, the Viking 1 lander touched down in the western reaches of Chryse Planitia (the "Golden Plain"), a large circular landform that lies 22.5 degrees north of the Martian equator.
It was the first-ever Mars landing for NASA. Viking 1, along with its twin Viking 2, went on to conduct the first fully successful mission on the Red Planet's surface. (The Soviet Union's Mars 3 probe survived its touchdown attempt on Dec. 2, 1971 but died less than two minutes later.) And those missions have left a rich and intriguing legacy.
The first color image ever captured on the surface of Mars. NASA's Viking 1 lander took this photo on July 21, 1976. (Image credit: NASA)
Viking 1 and Viking 2 — which touched down in a different Red Planet region on Sept. 3, 1976 — were sent to the surface to search for signs of life on Mars. (Each mission also featured an orbiter, which studied the planet from above.)
The landers did this using three different experiments, two of which returned negative results. But the third, called Labeled Release (LR), was different. LR observed a steady stream of carbon dioxide gas coming from dirt into which it had introduced nutrients — a possible sign of microbial metabolism.
Some scientists deemed the LR results a likely life detection. But most disagreed, ascribing them to abiotic reactions and stressing that, overall, the Viking data paint a picture of a dead planet.
That disagreement illustrates one of the main legacies of the Viking program: It showed researchers that hunting for extraterrestrial life is a complicated business, and they needed to learn more about Mars before attempting the search again on the Red Planet.
NASA didn't send a surface craft to Mars for another two decades, a hiatus caused in part by the Vikings' ambiguous results and high price tag, as well as a shifting of funds to the nascent space shuttle program.
The dry spell was broken in July 1997, when the agency's Pathfinder lander touched down in Chryse Planitia, about 530 miles (850 kilometers) from Viking 1. The main goals of Pathfinder's mission were to demonstrate a new "faster, better, cheaper" method of Mars exploration, prove out a new airbag-based landing system and get a mobile robot onto the red dirt.
Pathfinder achieved all of these objectives, notching the third by deploying a small rover named Sojourner. The little wheeled robot stumbled across rounded pebbles — strong evidence that they had been exposed to flowing water.
This discovery helped shape a new NASA Mars exploration strategy, one that aims to make an informed search for alien life after "following the water." Life as we know it depends on water, so the agency built rovers designed to hunt for signs of past liquid water and potentially habitable environments.
The twin golf-cart-sized rovers Spirit and Opportunity landed in 2004, and the car-sized Curiosity followed suit in August 2012. Then came Perseverance, which landed inside Mars' Jezero Crater in February 2021.
All of these wheeled explorers found evidence of past aqueous environments. Curiosity and Perseverance — with their more extensive and sophisticated scientific payloads — delved even deeper, discovering complex organic molecules that may have been produced by life as we know it.
The two latter rovers are continuing their work; both remain active on the Red Planet. (Pathfinder and Sojourner operated for about three months; Spirit was declared dead in 2010 and Opportunity fell victim to a Mars dust storm in 2018.)
Perseverance has collected a variety of Mars samples, which NASA wants to return to Earth for detailed study. As the Vikings' experience suggests, such a level of intense scrutiny may be necessary to make a definitive detection of life on Mars, if it indeed exists. (Getting those samples home is not a foregone conclusion, however; NASA's original plan was deemed too expensive, and it's now looking into a new return strategy.)
Perseverance also carried a little robotic companion, which heralded a new phase of Red Planet exploration — the Ingenuity helicopter.
Ingenuity was a technology demonstration, designed to show that rotorcraft could effectively ply the thin Red Planet skies. (Mars' atmosphere is just 1% as dense as that of Earth at sea level.)
The $80 million mission was a rousing success. The 4-pound (1.8 kilograms) Ingenuity was expected to make just five short hops on Mars but ended up flying 72 times over the course of nearly three years of activity. (Its first flight occurred on April 19, 2021, and its last was on Jan. 18, 2024.)
So NASA aimed higher, drawing up plans for future helicopter missions that could collect valuable scientific data. And such a mission is on course to launch in 2028, if all goes according to plan: Skyfall, which will send three Ingenuity-like choppers to Mars on a nuclear-powered rocket.
"Equipped with a suite of scientific instruments, these aerial scouts will map hidden ice deposits and analyze weather patterns," NASA officials wrote in a description of Skyfall. "The mission will also demonstrate how aerial vehicles can generate wide terrain and subsurface maps to identify safe and resource-rich destinations for future American astronauts venturing to Mars."
And Skyfall could be just another step toward even more ambitious aerial exploration on the Red Planet. NASA's Jet Propulsion Laboratory in Southern California, which built and operated Ingenuity, is looking into larger, more capable Mars helicopters that could do a wider variety of work on the Red Planet.
This is all part of Viking 1's legacy. That historic touchdown on Mars half a century ago lifted exploration up — all the way into the skies of another world.
NASA's Curiosity rover snapped this image on the surface of Mars, and scientists think it's the wreckage of an ancient sandstorm. (Image credit: NASA/JPL-Caltech/MSSS)
NASA's Curiosity rover has uncovered evidence of ancient sandstorms on the Red Planet.
What is it?
Scientists think ancient Mars was quite different than it is today. While we might know it now as a barred, reddish wasteland, billions of years ago it actually had an atmosphere. Scientists even think that it had flowing rivers and expansive lakes.
And with observations from the Curiosity rover, researchers are exploring ancient sandstorms they think blew across the Martian landscape.
In this image Curiosity snapped, you can see what experts think is the aftermath of an especially extreme sandstorm in a spot nicknamed "Jawbone Canyon." Winds from this storm were likely so extreme that they pushed sand into rippling waves that eventually hardened into rock.
And if you really look closely at this image, you can almost see how the rocks appear to have ripples on them.
While the image was captured in 2024, a new investigation of the observation and discovery of this sandstorm was described in a study published this year in the journal Geology.
Why is it incredible?
This observation by Curiosity is part of a long history of exploration on the Martian surface that actually began 50 years ago today.
On July 20, 1976, NASA's Viking 1 lander touched down on the Red Planet. Aside from the Soviet Mars 3 lander that lasted only a few seconds on the world before losing contact, Viking 1 was the first Mars lander to survive landing and successfully went on to study the planet.
Viking-1 took the first-ever images on the surface of Mars, studied the planet's soil and really sparked investigation of whether or not the world may have ever supported life. Thanks to the success of this mission 50 years ago, today we have rovers like Curiosity and Perseverance on Mars leading us at the cutting edge of exploration.
In looking back and commemorating the 50th anniversary of the Viking missions to Mars, one is struck by the bold and audacious undertaking.
Twin spacecraft missions — each consisting of a lander and an orbiter — made their way to Mars and into the history books. The Viking 1 lander planted its legs on the terrain of Chryse Planitia 50 years ago today, on July 20, 1976, while its Viking 2 counterpart touched down at Utopia Planitia on Sept. 3 of that year.
Among their duties, the dual landers scooped up the first soil samples of Mars and deposited those precious collectibles into onboard, specialized equipment. Viking scientists had designed that gear to help answer an intriguing question: Is there life on Mars?
A model of NASA's Viking 1 lander here on Earth. On July 20, 1976, the spacecraft touched down on the surface of Mars. (Image credit: NASA)
One of Viking's instruments was a GCMS, a combination of a gas chromatograph (GC) and a mass spectrometer (MS). A positive GCMS detection could confirm the possibility that organics needed for the origin of life as we know it were present.
After interpreting all the data and information gleaned from ingested Martian soil, most scientists at the time concluded that Viking relayed a "no life on Mars" result.
But is it possible that the two robots actually radioed back a very clear comeback: "Can you repeat the question?"
Different techniques
Ben Clark was a member of the Viking science team, and the instrument he designed made the first-ever measurements of the chemical composition of Mars soil. He is now a senior research scientist at the Space Science Institute in Boulder, Colorado.
"There were three life-detection experiments, each using different techniques to probe whether they could stimulate biological activity in the soil by adding various selected nutrients," Clark told Space.com. "Two were generally negative in their findings, but a third experiment had an expected strong response when it added nutrient."
Indeed, astrobiologist/inventor Gilbert Levin remained convinced that his Viking microbial detection instrument, called the Labeled Release experiment, did find living microorganisms in the soil of Mars. He held tight to that view until he passed in July 2021 at the age of 97.
Skeptical scientists
Clark recalled that many members of the scientific community were skeptical when geochemists pointed out that certain minerals can cause a similar response.
"Furthermore, when a second amount of nutrient was added, there was no additional response," Clark said. "Did the organisms die between experiments?"
Because of these responses, and especially because no organic molecules could be detected, most biologists concluded there was no life in the dirt that Viking tested. "However, there is also the question of whether the best nutrients were used in the Viking tests," Clark noted.
Microbiologists who study the small organisms that live in Earth soil, Clark added, know that some species are extremely adept at using sulfate as an energy source, by combining it with organics or with hydrogen gas.
"Unfortunately, none of the Viking life-detection experiments added hydrogen gas to their chambers," Clark said.
"Ironically, the instrument which searched for organics in the soil, the GCMS, used hydrogen gas in its analytical technique," he added. "Thus, there was a tank full of hydrogen gas located just centimeters away from the life-detection experiment package, but no connection between it and the GCMS where it was located."
This mosaic is made up of more than 100 images captured by NASA’s Viking 1 orbiter, which operated around Mars from 1976 to 1980. The scar across the center of the planet is the vast Valles Marineris canyon system. (Image credit: NASA/JPL-Caltech)
True positive detections?
Even today, there are some scientists who question whether some of the life-detection experimental results were in fact true positive detections, according to Clark.
"Other scientists believe that it was not enough to simply test the loose soil, but that life in fact may be just centimeters below the surface in areas where there is still ice in the ground," he said.
Clark said that no other planet in our solar system so closely matches the early history of our own planet Earth.
"Recent discoveries by the rovers now roaming Mars have revealed some detections of organic molecules, and even some so-called 'reduction spots,' which are interpreted by some geologists as evidence of activity of biological organisms," he said.
Misunderstood results
Steven Benner is an astrobiochemist and director of the Foundation for Applied Molecular Evolution in Alachua, Florida. He is author of the soon-to-be-issued "Meet the Neighbors: Life on Mars and How to Find It" (Penguin Press, 2026).
Benner has long argued that the results from Viking were misunderstood. He contends that the Red Planet remains an easily reached destination to discover a possible independent origin of life and draws upon the Viking records to spotlight how the scientific process has failed in this regard to date.
Tied to Viking's 50th anniversary, "I decided to write a grumpy 'take no prisoners' book that dispenses with politeness and focuses on the facts," Benner told Space.com.
Viking flyer from NASA Langley Research Center. The spacecraft were built by Martin Marietta with Langley in Hampton, Virginia managing the Viking project. The Jet Propulsion Laboratory handled the operations of the probes once in flight. (Image credit: Langley Research Center/The Viking Mars Missions Education and Preservation Project)
Misbegotten consensus
Benner said that his new book highlights two tales.
"Viking more likely than not found autotrophic microbial life on Mars, roughly 1,000 cells per gram — about what you might expect based on Earth analogs," said Benner.
The other story, he said, is that communities will defend a misbegotten "consensus" long after that consensus ceases to be defensible. They should not be beholden to a half century of mistakes, he emphasized.
The GCMS misinterpretation was 100% of the grounds for dismissing considerable life-positive data, according to Benner. So, he said, "we should then have gone back to the status quo ante, as Gil Levin did. But since 'consensus' in science is powerful, and Levin was polite, the community marginalized him."
Her late father, James Tillman, worked on Viking 1 and 2 and was a professor in the Department of Atmospheric Sciences at the University of Washington.
"There are a variety of reasons it's important to preserve Viking data," Tillman told Space.com. Archiving how and why things were done on Viking from an engineering standpoint is vital, she said, as is safeguarding the science data accumulated during the Viking program.
"Science is dynamic. Instruments and missions are finite in what they collect, so every data is part of a growing body of knowledge coming in pieces of a much larger puzzle. We can't complete the puzzle without all of the data," said Tillman. "So every facet of Mars science is a tiny piece of the puzzle. For that reason, we need to keep all the pieces."
This is true of every engineering success and failure, she added.
"Our organization has records on both. Because of that, we can help industry reduce costs by making the archives available on failed tests as much as successful ones," Tillman said.
It takes many, many missions to get close to answers we theorize on, she pointed out. "And then there is inspiration. By preserving the past — the who, what and how — we inspire youth and the public to support endeavors and even join the workforce," she concluded.
Space technicians prepare the Viking 1 lander, encased in its bioshield, for its sterilization. (Image credit: NASA)
Contaminate and confuse
"The entire Viking mission — orbiters and landers — are one of the most important sets of data about the planet Mars," said Barry DiGregorio, an honorary research fellow for the Buckingham Center for Astrobiology in the United Kingdom. He is author of "Mars: The Living Planet" (Frog Books/1997).
"Indeed, the Viking biology data have become more important today than they were during the Viking mission," said DiGregorio. "Because Viking carried the very first suite of extant biology instruments to Mars, extreme care was given to the extensive heat sterilization protocols for the Viking landers."
Those protocols ensured that the Vikings did not carry large numbers of terrestrial microorganisms that might contaminate and confuse the actual soil sample results in its three onboard life-detection instruments, DiGregorio said.
Warning flag
However, DiGregorio is also waving a warning flag.
The recent discovery of never-before-detected extremophile microbes in spacecraft assembly clean rooms has made it important to take planetary protection protocols to a new level, said DiGregorio.
"Unfortunately, the search for extant life on Mars has been made much more difficult by unwittingly sending Earth's hardiest extremophile microorganisms there for the last 30 years," he said.
If Mars life is indeed spotted, extra effort will be required "to make sure it isn't earthly extremophile microbes we are detecting," DiGregorio added.
Both Viking landers ceased operating more than four decades ago. But they could still aid the Mars life search today, according to DiGregorio. Perhaps, he said, "comparing any new data found with archived Viking Lander biology data will be crucial in determining their interpretation."
If you still picture Mars as a monotonous red desert, it may be time for an update.
The European Space Agency's Mars Express orbiter has been capturing some of the Red Planet's most surreal landscapes, and its latest images reveal a sprawling field that looks like molten metal frozen across the floor of an ancient Mars crater.
The shimmering "waves" aren't metal at all, however. They are dark sand dunes dusted with seasonal frost, much of it carbon dioxide, or "dry ice," that settles on the surface during Martian winters, giving the dunes their uncanny chrome-like sheen, according to ESA.
The rest is a trick of light and contrast. Because the dark sand absorbs light and the white frost reflects it, the interplay transforms the landscape into something that looks more like a scene from a sci-fi movie than a windswept Martian plain.
A bird's-eye view of wind-blown dunes in Kaiser Crater. (Image credit: ESA/DLR/FU Berlin)
Over thousands of years, Martian winds have sculpted this volcanic sand into dunes that now ripple through the floor of Kaiser Crater, a 129-mile-wide (207-kilometer-wide) impact basin in the planet's southern highlands. The bowl-shaped crater acts as a giant sand trap that prevents the sand from escaping, according to NASA.
The dunes themselves are darker than much of Mars' surface because they are made of fine, basaltic sand rich in volcanic minerals such as pyroxene and olivine, rather than the iron-oxide dust that gives the planet its familiar rusty-red appearance and its famous moniker, the Red Planet.
Because the crater floor remains visible between the ridges, scientists think there is a relatively limited sand supply shaping the field. Still, these ripples of sand are massive, extending for several kilometers and towering more than 100 meters (320 feet) above the surrounding terrain.
The landscape isn't just visually dramatic, it also preserves clues to a time when Mars was a very different world.
Today, Mars is wrapped in an atmosphere little more than a thin veil that is 100 times thinner than Earth's and slowly leaking into space. That makes it harder for winds to lift and transport sand than it is on our own planet. Yet the soaring dunes inside Kaiser Crater show that Martian winds have nonetheless been powerful enough to sculpt vast landscapes over time, perhaps during a period when the Martian atmosphere was thicker a few billion years ago.
The new image adds to a growing collection of striking Martian scenes captured by Mars Express, which has been orbiting the Red Planet since 2003. Just last month, the probe tracked a frenetic cluster of 30 dust devils swirling through the canyons of Mamers Valles, also in the northern hemisphere.
Over the spring and summer, the orbiter similarly spotlighted the planet's vast and complex geological history, from Shalbatana Vallis — carved by groundwater floods about 3.5 billion years ago into winding valleys that span the length of Italy — to a massive blanket of dark volcanic ash elsewhere on the world that has spread across a large chunk of the terrain over just the last 50 years, having either been redistributed by Martian winds or exposed as the overlying dust was blown away.
However desolate Mars may appear from afar, there is certainly no shortage of activity on its surface — or discoveries still waiting to be made.
NASA's Mars rover Curiosity spotted these "honeycomb" structures on Mars. (Image credit: NASA/JPL-Caltech/MSSS)
NASA's Curiosity rover has spotted a strange honeycomb texture on the surface of Mars. But what is it?
What is it?
Almost 14 years since landing on the Red Planet, Curiosity is still hard at work exploring. And in new observations, Curiosity has revealed an image that is certainly ... peculiar.
Curiosity went to get a closer look at an area first observed from Mars orbit, and found what appears to be a honeycomb structure in on the planet's surface. Polygonal shapes, nearly identical to one another, make up a pattern almost like a Martian wallpaper or carpet.
But what is it? Why does it look like that? What is a honeycomb doing on Mars?
Why is it incredible?
This is one of many mysteries we have yet to solve on Mars. While the team saw this area first from orbit around the planet, when the rover arrived and saw this structure they were surprised, they shared in a blog post.
In addition to the honeycomb texture, the area was littered with dark rocks and strewn around. But even these pebbles lack explanation. Did they "float" down from higher rock levels, did they launch out of Gale crater during some ancient collision or could they possibly even be meteorites from outside of Mars that ended up strewn across the surface? Researchers think any one of these explanations could be possible.
Previous, similar dark stones have been found on Mars with minerals like nickel that are common in meteorites and uncommon in Mars rocks. But are these similar? Perhaps part of a similar collision event? We don't yet know.
As researchers find new mysteries on Mars, they also continue to find new ways to investigate the unknown. With further study, they will explore both these strange honeycombs and the dark rocks scattered amongst them.
Deep oceans of magma once sloshed about inside the crust of Mars, seismic measurements taken by NASA's InSight mission suggest.
The marsquakes detected by InSight show a boundary 15 miles (24 kilometers) deep between two different types of rock that were formed by enormous pools of magma. The presence of these magma pools could completely change what we thought we knew about the early development of Mars.
Already, scientists say the discovery could change what we know about the history of Mars. "One of the big questions in planetary science is whether Earth is unique," said the University of Oxford's Jon Wade in a statement. "If Mars could develop this kind of complex crust without plate tectonics, then maybe the conditions needed for habitability can emerge on more planets than we realized, including those previously dismissed based on size or their apparent lack of tectonic activity."
Earth is shaped by plate tectonics, the shifting of giant slabs of the planet's crust above our planet's molten mantle in a motion that generates earthquakes and volcanoes, but which also creates new land and regulates atmospheric carbon by drawing it out of the atmosphere and re-releasing it though volcanic eruptions. This constant reprocessing results in a fairly complex crust with multiple layers.
However, no convincing evidence has been found that the Red Planet has ever had plate tectonics. Instead, it is what we call a 'stagnant lid' planet, where the entire crust is one unbroken layer. Beneath this solid lid, all the way down to the mantle 23.6 miles (38 km) below the Martian surface, was considered to be fairly homogenous.
But NASA's InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission, which operated on Mars's surface between 2018 and 2022, put this to the test. InSight's seismometer was designed to detect tremors from marsquakes triggered by meteorite impacts or shifts in the planet's interior. These seismic tremors would reverberate through Mars, and InSight could learn about the interior structure of the Red Planet based on how they reached the lander.
InSight's seismometer on the Martian surface. (Image credit: NASA/JPL–Caltech)
Thanks to the way these tremors passed through Mars's interior after traveling at different velocities through different kinds of rock, InSight discovered a boundary between two layers of crust, but its existence has not been explained until now.
Researchers at the University of Oxford tasked themselves with figuring it out. Using geothermal models and statistics, the Oxford team identified the two types of rock that best matched the seismic data. They conclude that above 15 miles (24 km) deep is a thick layer of mafic rock, which is rich in iron, magnesium and silica. Below this depth is denser, crystalline ultramafic rock, which contains iron and magnesium but is depleted in silica and which descends a further 8.7 miles (14 kilometers) to the boundary between the crust and the mantle.
It seems as though the rock has become differentiated – the denser material having settled out below the lighter mafic rock. This could only have happened in huge pools of magma that once resided in giant pockets within Mars's crust. Like oil separating from water, the mafic and ultramafic rock separated over time, in a process called differentiation, before the magma cooled and froze the layers in place.
The pockets of magma could have extended for hundreds and possibly even thousands of kilometers around the planet, each pool linked to the others. Giant volcanic systems on Mars such as Olympus Mons and the Tharsis volcanoes would not have been isolated hotspots, but would have been interconnected beneath the surface.
This is something of a surprise – this kind of 'transcrustal magmatism' has only ever been found on Earth before. It's evidence that even though Mars lacked plate tectonics, it could still have undergone a degree of geochemical evolution and deep, complex geology.
This geology could even have supported a habitable environment by regurgitating carbon back into the atmosphere to maintain a greenhouse effect. Because of its small size and therefore low gravity and lack of magnetic field, Mars's atmosphere is notoriously leaky, and over its history, much of its atmosphere – including large quantities of its precious water – has escaped into space.
Large-scale volcanism, powered by interconnected chambers of magma, could have belched greenhouse gases back into the atmosphere, thickening the Martian atmosphere and maintaining warmer temperatures for longer.
An illustration of InSight on Mars. (Image credit: NASA/JPL–Caltech)
But where did the magma come from? The Oxford team points the finger at upwelling from Mars' deep mantle, and with that magma came waves of heat that partially melted the crust, creating more magma. Both these processes took place on Earth during the Archaean Eon, which spanned between 4 and 2.5 billion years ago. On Earth, these processes contributed to the formation of the continents, although Mars' lack of plate tectonics and continents suggest that these processes were not as developed on the Red Planet.
Even so, some models suggest that mantle upwelling contributed to Mars' north–south dichotomy where the north contains mostly lowlands, which could have facilitated a large ocean, and the south is dominated by highlands.
"We've traditionally assumed that volcanism on Mars was relatively simple compared to that on Earth, but this discovery suggests that the planet could sustain massive, long-lived magmatic systems capable of evolving and reprocessing molten rock throughout the crust," said the study's lead author, Tobermory Mackay-Champion, who was previously at Oxford during the research but is now at the University of Bristol.
Mackay–Champion also highlights how this reprocessing of Mars's crust could have left metal deposits nearer the surface than had been thought.
"Mars may hold significantly more near-surface mineral wealth than previously recognized, boosting its potential for future mining, crewed missions and, eventually, permanent settlements," said Mackay-Champion.
While undoubtedly useful for a future outpost on Mars, this does raise the specter of companies pillaging and exploiting the Red Planet for its resources.
Could Martian mudstones be holding evidence of ancient microbes? New findings strengthen the case that the Red Planet once held life.
New data from NASA's Perseverance rover has revealed complex carbon in two Martian mudstones found in Mars' Jezero crater, the same location where previous evidence of possible ancient life has been found. Scientists think this macromolecular (meaning large) complex carbon, could hold evidence that ancient microbial life once existed in the same sedimentary material, according to one new paper describing these observations. "Measurements of two mudstones show hundreds of organic detections, making this the most robust organic detection in Jezero crater," the paper reads.
This comes soon after the news last year that Perseverance found what has been dubbed the strongest evidence of potential biosignatures, or hints of life, on Mars.
"Carbon is the primary building block for life on Earth, and all living things are made up of complex organic macromolecules," co-lead author Ashley Murphy, a researcher at the Planetary Science Institute, told Space.com. "On Earth, [macromolecular carbon] is often found in extremely old rocks and in some cases it is the only organic evidence of past microbial life.
"Since early Mars may have been more similar to Earth," Murphy added, "we may anticipate finding [macromolecular carbon] in old Martian rocks too, so we are searching for these organic macromolecules on Mars and other planetary bodies to determine whether the necessary chemical ingredients and environmental conditions to support life have ever existed there."
Perseverance landed on Mars in 2021 in Jezero Crater, an expansive crater thought to once be a lake that could have possibly harbored life. This landing site was in fact chosen because scientists thought it could have some of the best evidence for possible ancient life on the planet. And so far, in Perseverance's extensive explorations — which have now officially taken the rover the distance of a marathon on Mars — that prediction seems like it's turning out to be true.
In this new research, a team of scientists co-led by Murphy used Perseverance's spectrometer SHERLOC (the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals), which uses lasers to identify an area or object's chemical and mineral makeup, to map the distribution of organic matter in the individual mudstones. The crew found organic carbon inside two mudstones.
Furthermore, these carbon-filled mudstones were found in the same location as the last year's discovery of a potential biosignature found in a sedimentary rock on the Red Planet, which scientists say is still the strongest evidence that life could have once existed on early Mars. In this discovery, Perseverance found a rock now-named "Cheyava Falls" with distinctive "leopard spots."
These types of rock marking can be created in high heat or extremely acidic temperatures, but neither of these conditions are thought to have existed in the area. However, the markings can also be formed by the presence of life. So, while this rock wasn't conclusive evidence of past life on Mars, it certainly provided significant evidence that is now supported by this new data.
With these observations, the rover has made two main findings.
First, Perseverance has found organic, large, complex carbon in mudstones in Bright Angel, a rocky area on the northern and southern edges of Neretva Vallis, which is an ancient river valley in the Jezero area. And not only did Perseverance make hundreds of detections of organic carbon in these rocks, but the researchers also state that this is "the only detection of macromolecular carbon on a natural rock surface on Mars."
"This is also the first detection of MMC in a mudstone on Mars outside of Gale Crater, suggesting that the availability of organics may have been widespread across the planet billions of years ago," co-lead author Kyle Uckert, the SHERLOC deputy principal investigator at NASA's Jet Propulsion Laboratory, told Space.com.
A closeup of "leopard spots" on Mars seen by the Perseverance rover on the rock Cheyava Falls, which may show signs of a biosignature, but could also be from geologic processes. (Image credit: NASA/JPL-Caltech/MSSS)
While both studied mudstones have organic carbon in their interiors, according to these observations from Perseverance, there were some differences between the two rocks. The carbon in one mudstone was found mixed with primarily silicate minerals, while the other was filled with carbon mixed with secondary carbonate and sulfate minerals. The team also found that the carbon in both rocks was relatively intact, meaning the specimens might be resistant to radiation and oxidation or that it may have been recently exposed to the Martian surface.
Secondly, the team found that, in this identified carbon, Perseverance has detected evidence of potential biochemical interactions. These interactions left behind features in the two mudstones that look just like features created by microscopic life in sediments on Earth. This begs the question: Did ancient microbes on Mars really live in the sediments in this once-flowing river?
Maybe, maybe not. While that would certainly be one explanation, it's also possible that the carbon could have been created without life.
"There are multiple potential pathways to form abiotic organics on Mars," the authors state in this paper, clarifying that this, even compounded with other existing data, cannot conclusively say whether or not life created what Perseverance has observed.
"The science payload of the Perseverance rover was not designed to distinguish between abiotic and biotic processes, but was instead selected to identify compelling rocks to be collected for possible return to Earth for more rigorous testing," Uckert told Space.com. Uckert added that there could be many non-life reasons behind the presence of this complex carbon, "for example, it may have been delivered to the surface via meteoritic infall, or formed through hydrothermal geologic processes," he said.
For now, we can only wait until the next juicy bit of evidence about ancient life on Mars reveals itself.
This work was described in a paper published June 24 in the journal Science Advances.
