Nasa‘s Perseverance rover, due to launch to Mars this summer, will search an ancient crater lake for signs of past life. But if biology ever emerged on the Red Planet, how will scientists recognise it? Here, mission scientist Ken Williford explains what they’re looking for.
Today, Mars is hostile to life. It’s too cold for water to stay liquid on the surface, and the thin atmosphere lets through high levels of radiation, potentially sterilising the upper part of the soil.
But it wasn’t always like this. Some 3.5 billion years ago or more, water was flowing on the surface. It carved channels still visible today and pooled in impact craters. A thicker carbon dioxide (CO2) atmosphere would have blocked more of the harmful radiation.
Water is a common ingredient in biology, so it seems plausible that ancient Mars once offered a foothold for life.
In the 1970s, the Viking missions carried an experiment to look for present-day microbes in the Martian soil. But the results were judged inconclusive.
In the early 2000s, Nasa’s Mars Exploration Rovers were tasked with “following the water”. Opportunity and Spirit found extensive geological evidence for the past presence of liquid water.
The Curiosity rover, which touched down in 2012, found the lake that once filled its landing site at Gale Crater could have supported life. It also detected organic (carbon-containing) molecules that serve as life’s building blocks.
Now, the Perseverance rover will explore a similar environment with instruments designed to test for the signatures of biology.
“I would say it’s the first Nasa mission since Viking to do that,” said Ken Williford, the mission’s deputy project scientist, from Nasa’s Jet Propulsion Laboratory (JPL) in Pasadena, California.
“Viking was the search for extant life – that is, life that might be living on Mars today. Whereas the more recent Nasa approach has been to explore ancient environments because the data we have suggest that the earliest history of the planet tells us that Mars was most habitable during its first billion years.”
The target for Perseverance is Jezero Crater, where signs of a watery past are even clearer, when viewed from orbit, than those at Gale Crater.
The rover will drill into Martian rocks, extracting cores that are about the size of a piece of chalk. These will be sealed away – cached – in containers and left on the surface. These will be collected by another rover, sent at a later date, blasted into Mars orbit and delivered to Earth for analysis. It’s all part of a collaboration with the European Space Agency (Esa) called Mars Sample Return.
Jezero features one of the best-preserved Martian examples of a delta: layered structures formed when rivers enter open bodies of water and deposit rocks, sand and – potentially – organic carbon.
“There’s a river channel flowing in from the west, penetrating the crater rim; and then just inside the crater, at the river mouth, there’s this beautiful delta fan that’s exposed. Our plan is to land right in front of that delta and start exploring,” said Dr Williford.
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The delta contains sand grains originating from rocks further upstream, including a watershed to the north-west.
“The cement between the grains is very interesting – that records the history of the water interacting with that sand at the time of the delta deposition in the lake,” says Ken Williford.
“It provides potential habitats for any organisms living between those grains of sand. Bits of organic matter from any organisms upstream could potentially be washed in.”
Jezero is located in a region that has long been of interest to science. It’s on the western shoulder of a giant impact basin called Isidis, which shows the strongest Martian signals of the minerals olivine and carbonate as measured from space. “Carbonate minerals are one of the key targets that led us to explore this region,” says Ken Williford.
A survey of the minerals in Jezero Crater by Dr Briony Horgan of Purdue University, Dr Melissa Rice of Western Washington University (both scientists on the mission) and colleagues, revealed carbonate deposits at the western edge of the ancient shore. These “marginal carbonates” were likened to a bathtub ring – the build-up of soap scum that’s left after the water is drained.
Terrestrial carbonates can lock up biological evidence within their crystals. They can even help form structures that are hardy enough to survive as fossils for billions of years, including seashells, coral and stromatolites.
Stromatolites are formed by many millimetre-scale layers of bacteria and sediment that build up over time into larger structures, sometimes shaped like domes. On Earth, they occur along ancient shorelines, where sunlight and water are plentiful.
Billions of years ago, Jezero’s shore was exactly the kind of place where stromatolites could have formed – and have been preserved – making the carbonate-rich bathtub ring a prime target for the mission.
The rover’s scientific payload will help investigate these questions and others.
Two zoom cameras on the rover’s mast – part of the Mastcam-Z system – will survey the landscape, sending back information about the colours, structures and textures.
From several metres away, an instrument called Supercam will fire a laser at rocks to get a measure of their elemental and mineral composition.
This will help scientists select “parking places” where they can deploy the robotic arm. The arm’s drill is used to wear down and flatten a 4.5cm circular patch of rock. The turret – or end – of the arm is then turned around.
An instrument called Sherloc captures images of the flat area and produces a detailed map of the minerals present, including any organics. Another instrument called Pixl will then give scientists the detailed elemental, or chemical, composition of the same area.
Within this data-set, scientists will “look for concentrations of biologically important elements, minerals and molecules – including organic matter. In particular, [it’s] when those things are concentrated in shapes that are potentially suggestive of biology”, says Ken Williford.
Drawing together many lines of evidence is vital; visual identifications alone won’t be enough to convince scientists of a biological origin, given the high bar for claims of extra-terrestrial life. Short of a huge surprise, finds are likely to be described only as potential biosignatures until rocks are sent to Earth for analysis.
Referring to stromatolites, Dr Williford explains: “The layers tend to be irregular and wrinkly, as you might expect for a bunch of microbes living on top of each other. That whole thing can fossilise in a way that’s visible even to the cameras.
“But it’s when we see shapes like that and, maybe, one layer has a different chemistry than the next, but there is some repeating pattern, or we see organic matter concentrated in specific layers – those are the ultimate biosignatures that we might hope to find.”
Yet, Mars might not give up its secrets easily. In 2019, scientists from the mission visited Australia to familiarise themselves with fossil stromatolites that formed 3.48 billion years ago in the country’s Pilbara region.
“We will have to look harder [on Mars] than when we went to the Pilbara… our knowledge of their location comes from many decades of many geologists going year-after-year and mapping the territory,” says Ken Williford.
On Mars, he says, “we are the first ones”.
A mineral called hydrated silica also seems to be present near the delta. Its properties also make it good at preserving signs of life, including “microfossils” – the minuscule remains of bacteria, fungi or plants.
On Earth, we can detect fossilised microbes at the level of individual cells. But in order to see them, scientists have to cut out a slice of rock, grind it to within the thickness of a sheet of paper and study it on a glass slide.
No rover can do this. But, then, it might not have to.
“It’s very rare to find an individual microbe hanging out on its own,” says Dr Williford.
“Back when they were alive – if they were anything like Earth microbes – they would have joined together in little communities that build up into structures or clumps of cells that are detectable to the rover.”
After exploring the crater floor, scientists want to drive the rover up onto the rim. Rock cores taken here, when analysed on Earth, could provide an age for the impact that carved out the crater and a maximum age for the lake.
But there’s another reason for being interested in the crater rim. When a large space object slams into rocks containing water, the huge energy can set up hydrothermal systems – where hot water circulates through the rocks. The hot water dissolves minerals from the rocks that provide the necessary ingredients for life.
“If that happened, that would have been the first habitable environment at Jezero Crater,” says Ken Williford. The evidence – along with signs of any life that colonised the environment – could be preserved up on the rim.
The current mission scenario foresees the rover driving to the nearby north-east Syrtis region as an “aspirational goal”.
It’s more ancient even than Jezero and also holds the promise of exposed carbonates – which may have formed in a different way to those in the crater.
If, by the end of this mission, signs of past life haven’t presented themselves, the search won’t be over. The focus will turn to those cores, waiting for delivery to Earth.
But the exciting prospect remains that the mission might not just throw up more questions, but answers too. That outcome could be planet-shaking. Whatever lies in wait for plucky Perseverance, we are on the verge of a new phase in our understanding of Earth’s near-neighbour.
More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.
That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.
“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”
The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.
Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.
Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.
Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.
Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.
Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.
“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”
The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.
North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.
Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”
Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.
Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.
For Dello, the “fingerprints of climate change” were clear.
“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”
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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.
On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.
They call it “Big Sam.”
The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.
It didn’t die alone.
“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.
She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”
“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.
The head alone, she said, is about the size of a baby elephant.
The discovery was a long time coming.
The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.
“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.
When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”
“It contains about 100 to 300 bones per square metre,” she said.
Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.
About a year ago, they found the second adult: Big Sam.
Bamforth said both dinosaurs are believed to have been the elders in the herd.
“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.
“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”
The genders of the two adults are unknown.
Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.
The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.
She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.
“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.
“It’s pretty exciting.”
This report by The Canadian Press was first published Sept. 25, 2024.
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
