It is notorious for its role in the expansion and continuation of American slavery, and for its adverse health effects. The latter includes cardiovascular disease and various cancers, including lung cancer, the most common malignancy, underlying millions of deaths each year.
Health officials, attorneys, and activists have spent decades targeting its industrial cultivators in an effort to limit its advertising and sale, particularly to minors. Read More
I look at rocks on Mars for a living—a lot of rocks. Because of this, I’ve gotten pretty good at knowing what to expect and what not to expect when analyzing the chemical make-up of a Martian rock. You expect to find lots of basalt, the building block of all planets.
What I didn’t expect were large amounts of manganese. So when my colleagues and I found exactly that on a Martian rock called “Caribou” back in 2013, we thought, “This has to be a mistake.”
Trace amounts of the element manganese typically exist in basalt. To get a rock with as much manganese as Caribou has, the manganese needs to be concentrated somehow. The rock has to be dissolved in liquid water that also has oxygen dissolved in it.
If conditions are right, the manganese liberated from the rock can then precipitate as manganese oxide minerals. On Earth, dissolved oxygen in groundwater comes from our atmosphere. We’ve known for some time now that Mars once had vast oceans, lakes and streams. If we could peer onto Mars millions of years ago, we’d see a very wet world. Yet we didn’t think Mars ever had enough oxygen to concentrate manganese—and that’s why we thought the data from Caribou must have been an error.
So what do you do when you find a Martian rock with a chemistry you didn’t expect? You go look for more.
When NASA’s Curiosity rover arrived at the Kimberly region of Gale crater, we went to work, looking at the mineral-filled cracks in sandstones on the floor of what was once a deep lake. We used the ChemCam instrument, which sits atop Curiosity and was developed here at Los Alamos National Laboratory, to “zap” rocks on Mars and analyze their chemical make-up. (In less than four years since landing on Mars, ChemCam has analyzed roughly 1,500 rock and soil samples.)
When ChemCam fires its laser pulse, it vaporizes an area the size of a very small pinhead. The system’s telescope on the rover peers at the flash of glowing plasma created by the vaporized material and records the colors of light contained within it. This light allows us here on Earth to determine the elemental composition of the vaporized material.
And what did ChemCam discover? More rocks filled with manganese oxides. So Caribou was not a mistake — far from it.
We never expected to find manganese oxides on Martian rocks because we didn’t think Mars ever had the right environmental conditions to create them. We can look to Earth’s geological record for an explanation. More than 3 billion years ago, Earth had lots of water but no widespread deposits of manganese oxides until after photosynthesizing microbes raised the oxygen levels in our atmosphere.
Although there was already plenty of other microbial life on Earth at this time, these new photosynthetic microbes used sunlight energy in a new way and created a new type of waste product in the process: oxygen.
By adding oxygen to the atmosphere, these tiny microbes transformed Earth’s environment. Suddenly, minerals never before formed on Earth started being deposited, including manganese oxides. This monumental environmental shift is recorded in the chemistry of rocks of that age all over the world. Earth has never been the same since. (Some hypothesize that more complex life forms, such as humans, might never have developed without this atmospheric change.)
So to summarize: In the Earth’s geological record, the appearance of high concentrations of manganese marks a major shift in our atmosphere’s composition, from relatively low oxygen abundances to the oxygen-rich atmosphere we see today. The presence of the same types of materials on Mars suggests that something similar happened there. If that’s the case, what formed that oxygen-rich environment?
One way oxygen could have gotten into the Martian atmosphere is from the breakdown of water when Mars was losing its magnetic field.
Without a protective magnetic field to shield the surface from ionizing radiation, that radiation split water molecules into hydrogen and oxygen. Mars’ relatively low gravity couldn’t hold onto the very light hydrogen atoms, but the heavier oxygen atoms remained behind. Rocks absorbed much of this oxygen, leading to the rusty red dust that covers the surface today. While Mars’ famous red iron oxides require only a mildly oxidizing environment to form, manganese oxides require a strongly oxidizing environment. Finding manganese oxides suggests that past conditions were far more oxidizing than previously thought.
NASA’s Opportunity rover, which has been exploring Mars since 2004, also recently discovered high-manganese deposits in its landing site thousands of miles from Curiosity, which supports the idea that the conditions needed to form these materials were present well beyond Gale crater.
Of course, it’s hard to confirm whether the ionizing-radiation scenario I’ve presented here for creating Martian atmospheric oxygen actually occurred. But it’s important to note that this idea represents a departure in our understanding of how planetary atmospheres might become oxygenated. So far, abundant atmospheric oxygen has been treated as a so-called biosignature, or a sign of existing life.
The next step in this work is for scientists to better understand the relationship between manganese minerals and life. On Earth, they are highly related—but they certainly don’t need to be.
So how can we tell whether the manganese on Mars might actually be made by microbes? The answer is lots and lots of laboratory experiments. If it’s possible to distinguish between manganese oxides produced by life and those produced in a non-biological setting, we can apply that knowledge directly to Martian manganese observations to better understand their origin.
In the meantime, we’ll keep our eyes trained on the Martian surface and see what other secrets it has to reveal.
Nina Lanza is a staff scientist at Los Alamos National Laboratory, which has built and operated more than 500 spacecraft instruments for national defense. That background gives the Laboratory the expertise to develop discovery-driven instruments like ChemCam and its souped-up successor, SuperCam, also developed by the Laboratory and scheduled for the Mars 2020 rover mission.
When we talk of the history of computers, most of us will refer to the evolution of the modern digital desktop PC, charting the decades-long developments by the likes of Apple and Microsoft. What many don’t consider, however, is that computers have been around much longer. In fact, they date back millennia, to a time when they were analogue creations.
Today, the world’s oldest known “computer” is the Antikythera mechanism, a severely corroded bronze artifact which was found at the beginning of the 20th Century, in the remains of a shipwreck near the Mediterranean island of Antikythera. It wasn’t until the 1970s that the importance of the Antikythera mechanism was discovered, when radiography revealed that the device is in fact a complex mechanism of at least 30 gear wheels. Read More
Forty years ago today, the first of two landing probes of NASA’s Project Viking touched down on planet Mars.
Discover contributor Dr. David Warmflash spoke with Dr. Gilbert Levin, whose Labeled Release (LR) experiment was one of three instruments delivered by the Viking landers to look for Martian microorganisms in 1976.
At age 92, Levin is the only survivor of the three biology experimenters and he’s looking ahead to 2020 when he hopes to have another instrument on the Martian surface looking for life. Read More
On Easter Island, isolated in the middle of the vast Pacific Ocean, ten species of near microscopic insects are all that remain of the island’s native species — at least for now.
Hidden in volcanic caves that dot the island, the endemic insects of Rapa Nui eke out an existence in an increasingly imperiled habitat. Their ancestral homes, fragile gardens of moss and ferns, are endangered by tourists flooding into the tiny island, and hordes of invasive species threaten to crowd them out. The island may have been immortalized by its iconic Moai, monolithic stone statues standing some 40 feet tall, but its most important inhabitants are almost too small to be seen. Read More
When Psy’s “Gangnam Style” broke YouTube, they refused to give it a single view.
When people soaked themselves during the ALS Ice Bucket Challenge, they called it a waste of water.
When Pokémon Go took the United States by storm after its release July 6, they went out of their way to tell friends, family and social network followers they would never play the game. They encouraged pocket monster trainers to grow up, pursue gainful employment or just get off their lawns. One writer, Mattie Lou Chandler, was compelled to publish “A Hater’s Guide to Pokémon Go.” Read More
A new paper reports that over half of Earth’s land area has suffered biodiversity loss beyond “safe limits.”
The study, released Thursday in Science, compiles a global dataset of biodiversity change and compares it to human land use patterns. The analysis shows that 58 percent of Earth’s land, which is home to 71 percent of the human population, has surpassed a recently proposed safe limit for biodiversity loss, beyond which ecosystems may no longer support human societies.
While the news sounds dire, other ecologists contend that the very notion of setting “safe limits” is a danger in itself, and criticize this line-in-the-sand approach to assessing the planet’s ecological health. In fact, critics say setting a limit may do more harm than good. Read More
Most of us harbor about 2 percent Neanderthal DNA, inherited when our ancestors bred with Neanderthals more than 50,000 years ago. This was revealed back in 2010, when geneticists salvaged enough fragments of ancient DNA from Neanderthal bones to piece together a full genome. The discovery squelched a longstanding debate over whether Neanderthals and modern humans met — they did — and mated — oh yeah.
But why do we only have 2 percent Neanderthal ancestry? And what are the effects of that Neanderthal DNA on living humans? And why did our ancestors survive and Neanderthals go extinct? We’ve attributed our supremacy to bigger brains, better diets and advanced technology, but there may be a subtler, less flattering explanation for our evolutionary success. Read More
Since the evolution of dogs from wolves tens of thousands of years ago, they have been selectively bred for various roles as guards, hunters, workers and companions. But dogs are not the only animal humans have domesticated, which suggests that although dogs get all the attention, there’s reason to argue other species could also deserve the title of “man’s best friend”.
Anthrozoology, the study of human-animal relationships, has established that dogs demonstrate complex communication with humans. Charles Darwin thought that dogs experienced love, but it was only in 2015 that Japanese scientists demonstrated what we all intuitively knew. Miho Nagasawa and colleagues sprayed the “love hormone” oxytocin up dogs’ noses, measured the loving gaze between dog and human, and then measured the oxytocin levels in the humans’ urine, finding them to be higher. Rest assured, dog owners, that science has verified your bond with your faithful hound. Read More
At the turn of the twentieth century, a young Thorleif Schjelderup-Ebbe began vacationing with his wealthy parents, both sculptors, at a country retreat outside Kristiania (now Oslo), Norway, where he immersed himself in the lives of birds in the barnyard.
He gave them names, closely watched how they behaved, and learned how to recognize one from the other. He “became terribly interested in chickens, terribly interested,” Schjelderup-Ebbe’s son Dag recounted in 1986 in an interview published in Human Ethology Bulletin. Read More