You can imagine that popping maize kernels was first discovered by accident. Some maize probably fell into a cooking fire, and whoever was nearby figured out that this was a handy new way of preparing the food. 
| Photo Credit: pexels.com

You have to wonder how people originally figured out how to eat some foods that are beloved today. The cassava plant is toxic if not carefully processed through multiple steps. Yogurt is basically old milk that’s been around for a while and contaminated with bacteria. And who discovered that popcorn could be a toasty, tasty treat?

These kinds of food mysteries are pretty hard to solve. Archaeology depends on solid remains to figure out what happened in the past, especially for people who didn’t use any sort of writing. Unfortunately, most stuff people traditionally used made from wood, animal materials or cloth decays pretty quickly, and archaeologists like me never find it.

We have lots of evidence of hard stuff, such as pottery and stone tools, but softer things – such as leftovers from a meal – are much harder to find. Sometimes we get lucky, if softer stuff is found in very dry places that preserve it. Also, if stuff gets burned, it can last a very long time.

Corn’s ancestors

Luckily, corn – also called maize – has some hard parts, such as the kernel shell. They’re the bits at the bottom of the popcorn bowl that get caught in your teeth. And since you have to heat maize to make it edible, sometimes it got burned, and archaeologists find evidence that way. Most interesting of all, some plants, including maize, contain tiny, rock-like fragments called phytoliths that can last for thousands of years.

Scientists are pretty sure they know how old maize is. We know maize was probably first farmed by Native Americans in what is now Mexico. Early farmers there domesticated maize from a kind of grass called teosinte.

Before farming, people would gather wild teosinte and eat the seeds, which contained a lot of starch, a carbohydrate like you’d find in bread or pasta. They would pick teosinte with the largest seeds and eventually started weeding and planting it. Over time, the wild plant developed into something like what we call maize today. You can tell maize from teosinte by its larger kernels.

There’s evidence of maize farming from dry caves in Mexico as early as 9,000 years ago. From there, maize farming spread throughout North and South America.

Popped corn, preserved food

Figuring out when people started making popcorn is harder. There are several types of maize, most of which will pop if heated, but one variety, actually called “popcorn,” makes the best popcorn. Scientists have discovered phytoliths from Peru, as well as burned kernels, of this type of “poppable” maize from as early as 6,700 years ago.

You can imagine that popping maize kernels was first discovered by accident. Some maize probably fell into a cooking fire, and whoever was nearby figured out that this was a handy new way of preparing the food. Popped maize would last a long time and was easy to make.

Ancient popcorn was probably not much like the snack you might munch at the movie theater today. There was probably no salt and definitely no butter, since there were no cows to milk in the Americas yet. It probably wasn’t served hot and was likely pretty chewy compared with the version you’re used to today.

It’s impossible to know exactly why or how popcorn was invented, but I would guess it was a clever way to preserve the edible starch in corn by getting rid of the little bit of water inside each kernel that would make it more susceptible to spoiling. It’s the heated water in the kernel escaping as steam that makes popcorn pop. The popped corn could then last a long time. What you may consider a tasty snack today probably started as a useful way of preserving and storing food.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Neanderthals, the closest cousins of modern humans, lived in parts of Europe and Asia until their extinction some 30,000 years ago.

Genetic studies are revealing ever more about the links between modern humans and these long-gone relatives – most recently that a rush of interbreeding between our species occurred in a relatively short burst of time around 47,000 years ago. But one mystery still remains.

The Homo sapiens genome today contains a little bit of Neanderthal DNA. These genetic traces come from almost every part of the Neanderthal genome – except the Y sex chromosome, which is responsible for making males.

So what happened to the Neanderthal Y chromosome? It could have been lost by accident, or because of mating patterns or inferior function. However, the answer may lie in a century-old theory about the health of interspecies hybrids.

Neanderthal sex, genes and chromosomes

Neanderthals and modern humans went their separate ways somewhere between 550,000 and 765,000 years ago in Africa, when Neanderthals wandered off into Europe but our ancestors stayed put. They would not meet again until H. sapiens migrated into Europe and Asia between 40,000 and 50,000 years ago.

Scientists have recovered copies of the full male and female Neanderthal genomes, thanks to DNA from well-preserved bones and teeth of Neanderthal individuals in Europe and Asia. Unsurprisingly, the Neanderthal genome was very similar to ours, containing about 20,000 genes bundled into 23 chromosomes.

Like us, they had two copies of 22 of those chromosomes (one from each parent), and also a pair of sex chromosomes. Females had two X chromosomes, while males had one X and one Y.

Y chromosomes are hard to sequence because they contain a lot of repetitive “junk” DNA, so the Neanderthal Y genome has only been partially sequenced. However, the large chunk that has been sequenced contains versions of several of the same genes that are in the modern human Y chromosome.

In modern humans, a Y chromosome gene called SRY kickstarts the process of an XY embryo developing into a male. The SRY gene plays this role in all apes, so we assume it did for Neanderthals as well – even though we haven’t found the Neanderthal SRY gene itself.

Interspecies mating left us with Neanderthal genes

There are lots of little giveaways that mark a DNA sequence as coming from a Neanderthal or a H. sapiens. So we can look for bits of Neanderthal DNA sequence in the genomes of modern humans.

The genomes of all human lineages originating in Europe contain about 2% Neanderthal DNA sequences. Lineages from Asia and India contain even more, while lineages restricted to Africa have none. Some ancient Homo sapiens genomes contained even more – 6% or so – so it looks like the Neanderthal genes are gradually fading out.

Most of this Neanderthal DNA arrived in a 7,000-year period about 47,000 years ago, after modern humans came out of Africa into Europe, and before Neanderthals became extinct about 30,000 years ago. During this time there must have been many pairings between Neanderthals and humans.

At least half of the whole Neanderthal genome can be pieced together from fragments found in the genomes of different contemporary humans. We have our Neanderthal ancestors to thank for traits including red hair, arthritis and resistance to some diseases.

There is one glaring exception. No contemporary humans have been found to harbour any part of the Neanderthal Y chromosome.

What happened to the Neanderthal Y chromosome?

Was it just bad luck that the Neanderthal Y chromosome got lost? Was it not very good at its job of making males? Did Neanderthal women, but not men, indulge in interspecies mating? Or was there something toxic about the Neanderthal Y so it wouldn’t work with human genes?

A Y chromosome comes to the end of the line if its bearers have no sons, so it may simply have been lost over thousands of generations.

Or maybe the Neanderthal Y was never present in interspecies matings. Perhaps it was always modern human men who fell in love with (or traded, seized or raped) Neanderthal women? Sons born to these women would all have the H. sapiens form of the Y chromosome. However, it’s hard to reconcile this idea with the finding that there is no trace of Neanderthal mitochondrial DNA (which is limited to the female line) in modern humans.

Or perhaps the Neanderthal Y chromosome was just not as good at is job as its H. sapiens rival. Neanderthal populations were always small, so harmful mutations would have been more likely to accumulate.

We know that Y chromosomes with a particularly useful gene (for instance for more or better or faster sperm) rapidly replace other Y chromosomes in a population (called the hitchhiker effect).

We also know the Y chromosome is degrading overall in humans. It is even possible that SRY was lost from the Neanderthal Y, and that Neanderthals were in the disruptive process of evolving a new sex-determining gene, like some rodents have.

Was the Neanderthal Y chromosome toxic in hybrid boys?

Another possibility is that the Neanderthal Y chromosome won’t work with genes on other chromosomes from modern humans.

The missing Neanderthal Y may then be explained by “Haldane’s rule”. In the 1920s, British biologist J.B.S. Haldane noted that, in hybrids between species, if one sex is infertile, rare or unhealthy, it is always the sex with unlike sex chromosomes.

In mammals and other animals where females have XX chromosomes and males have XY, it is disproportionately male hybrids that are unfit or infertile. In birds, butterflies and other animals where males have ZZ chromosomes and females have ZW, it is the females.

Many crosses between different species of mice show this pattern, as do feline crosses. For example, in lion–tiger crosses (ligers and tigons), females are fertile but males are sterile.

We still lack a good explanation of Haldane’s rule. It is one of the enduring mysteries of classic genetics.

But it seems reasonable that the Y chromosome from one species has evolved to work with genes from the other chromosomes of its own species, and might not work with genes from a related species that contain even small changes.

We know that genes on the Y evolve much faster than genes on other chromosomes, and several have functions in making sperm, which may explain the infertility of male hybrids.

So this might explain why the Neanderthal Y got lost. It also raises the possibility that it was the fault of the Y chromosome, in imposing a reproductive barrier, that Neanderthals and humans became separate species in the first place.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

It was the kind of task any competent seamstress has completed hundreds of times before: altering denim jeans and jerseys. But there was something different about this piece of work. Though our team of scientists were paying for it, we weren’t her ultimate customers – the clothes were to be worn by dead pigs.

The pigs and their specially tailored outfits were central to research conducted by ourselves, Devin Finaughty and our colleagues from South Africa’s University of Cape Town (UCT), a group of forensic scientists known as taphonomists. We study the environmental forces that drive changes to a body after death. A key aspect is estimating time-since-death, the length of time between death and a body being recovered. Ascertaining this detail can help to identify the person and reconstruct the circumstances around their death.

Legal and ethical challenges prohibit taphonomic research using donated human remains in most countries. Currently, human taphonomic facilities only exist in the US, the Netherlands, Australia and Canada. These facilities have been proposed in other countries, including the UK and India, but have not overcome legal and public resistance.

These human facilities are not legal in South Africa, and as a result pigs are used. Pigs, specifically those weighing around 60kg, are useful for human decomposition studies because they have anatomical similarities to humans. They have been used in taphonomic research since the 1980s.

But it’s not just the human body that decomposes after death. Clothing degrades too and, to obtain forensically realistic information, clothing tailored to the body is required. That’s why a seamstress was so central to this study. Once the alterations were done, we dressed six pig carcasses and left them to decompose in two forensically significant Cape Town habitats, one in Delft at the South African Medical Research Council’s research facility and one in a secure area in the suburb of Rosebank.

We found, overall, that winter-season clothing delayed decomposition. Summer-season clothing accelerated the process. Carcass weight loss was directly affected by the scavenging of the Cape grey mongoose (Galerella pulverulenta), which accelerated the decomposition rate. And single carcasses within the same habitat decomposed faster than when two or more carcasses are dumped together.

These findings have helped deepen our understanding of how soft tissue desiccates (dries out or mummifies), which is central to improving the accuracy of time-since-death estimations and can assist in criminal investigations.

A unique experiment

This study, which was part of Dr Adams’ PhD, is the latest conducted by our research team, which has been collecting data since 2014. The team has years of local data; for instance, we were the first to show that mongoose scavenge from bodies.

In this experiment we focused on mummification. This isn’t the process you might associate with ancient Egyptian practices. Cape Town summers are hot with dry winds; this can produce a rare natural phenomenon known as precocious mummification. This occurs when the body desiccates in less than 30 days through the gradual removal of moisture from tissues. It is usually the result of climatic extremes, such as in an arid desert, and hot, dry micro-environments, such as in a sealed house.

The phenomenon was first documented in Cape Town only in 2019 by members of our team. Our new experiment sought to build on those findings by analysing the specific environmental driving forces of desiccation in Cape Town. Courts of law prefer quantifiable data with low levels of subjectivity, so this is critical for justice.

Clothing was a key part of this experiment. That’s because most of the dead bodies found outdoors in the Cape Town area are dressed in seasonally appropriate clothing.

The majority of these cases involve a single deceased person. We chose clothing for the pig carcasses based on a previous survey of the most common items found in actual local forensic cases.

Sensors gather rich data

An electrical engineer at UCT, Justin Pead, helped us design and develop sensors that were inserted into the pig bodies (one in the head, one in the neck and one in the lower body). These devices measure tissue resistivity at various depths within decomposing bodies, which is related to the drying out of the tissue.

The sensors were tested across two summer seasons and one winter. The data they collected illustrate the complex interplay between environmental conditions and mummification processes.

In the high heat of summer, the body rapidly desiccated, with tissues gradually losing moisture until reaching a state of mummification in under 30 days. In the coolness of winter, the bodies reached a stage of advanced decomposition and lost about 20kg of their initial weight but never lost any more weight and never reached the skeleton stage. The colder temperatures and higher humidity levels prevented them from drying out. Cape Town has rainy, stormy conditions in winter.

A global first

Measuring desiccation for estimating time-since-death opens new avenues for research. It has implications for several disciplines. Forensic anthropologists, forensic taphonomists, electrical engineers and statisticians all have a role to play.

Our approach also offers the court system some more objective data.

The integration of innovative methodologies and technologies, such as the use of sensors on custom-designed printed circuit boards inserted in decomposing tissue, is especially exciting. It promises to change forensic taphonomy practices and enhance understanding of postmortem processes everywhere.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

A motorcycle drives between baobab trees at baobab alley near the city of Morondava, Madagascar, August 30, 2019.
| Photo Credit: Reuters

The baobab tree is a distinctive sight on the landscape. When its contorted branches are leafless during the dry season, they resemble jumbled roots emanating from a thick trunk, making it appear as if someone had yanked the tree from the ground, flipped it on its head and jammed it back into the earth.

Hence one of its nicknames: the “upside down tree.” But the origins and history of the baobab – found in Madagascar and parts of Africa and Australia – have been something of a mystery. A new study resolves this, based on genomic analyses of all eight recognized species as well as ecological and geological data, so the baobab’s story can finally be told.

The baobab lineage originated in Madagascar roughly 21 million years ago and reached Africa and Australia sometime in the past 12 million years, the researchers found. Madagascar, an island off Africa’s southeastern coast, is a biodiversity hot spot and home to an assemblage of unusual flora and fauna.

Two baobab lineages went extinct in Madagascar, but not before establishing themselves elsewhere, one in Africa and one in Australia, the study showed.

The tale of how a tree crossed the Indian Ocean to put down roots in two distant destinations is dramatic. It appears that baobab seed pods floated from Madagascar to mainland Africa, located about 250 miles (400 km) to the west, and to Australia, situated more than 4,000 miles (nearly 7,000 km) to the east.

“The plants almost certainly got to Africa and Australia floating on or with vegetation rafts,” said botanist Tao Wan of the Wuhan Botanical Garden in China, one of the authors of the study published on Wednesday in the journal Nature.

“The long-distance dispersal to Australia was probably facilitated by the Indian Ocean gyre, which is an oceanic current that circulates south past Madagascar, where it probably picked up baobab seed pods, before the current swings east to Australia, where it delivered the pods. The current then circulates north and then swings west past Mauritius and to Africa once again, where it completes the gyre,” Wan added.

Baobabs, found in dry savannah habitats, provide food, shelter and nesting sites for wildlife, from bees to birds to various mammals. Their fruits also provide valuable nutrients and medicines for people, and baobab leaves are edible, too.

The trees produce large, night-flowering, sweet-smelling flowers whose sugary nectar attracts nocturnal pollinators including fruit bats and hawk moths, as well as two types of primates, lemurs in Madagascar and bush babies in Africa.

“They can reach huge dimensions – depending on the species – in both height and diameter, and are reported to live for thousands of years. The root systems are also massive, which are considered to play an important ecological role, helping to slow down soil erosion and enabling nutrient recycling,” said plant geneticist and study co-author Ilia Leitch of the Royal Botanic Gardens Kew in London.

“The trees have astonishing and distinctive growth forms, some species with massive trunks that are hollow cylinders of low-quality wood ramified with many water-filled living cells. Some of the largest and oldest trees in Australia have been estimated to hold more than 100,000 liters (26,400 gallons) of water,” said botanist and study co-author Andrew Leitch of Queen Mary University of London.

They represent a water source for local people during the dry season. But Africa’s baobabs are vulnerable to elephant damage because the animals sometimes gouge the tree trunks with their tusks to get water.

The tree has become part of folklore.

“The people of Kafue in Africa have a legend that four beautiful maidens used a tree for shade and the tree fell in love with them,” Wan said. “But the maidens fell in love with humans, so the tree got jealous and imprisoned them in its trunk, where they remain to this day. People say you can hear them still, I guess because the hollow center acts as some sort of sound chamber in some trees.”

People walk on an overpass past office towers in the Lujiazui financial district of Shanghai, China October 17, 2022.
| Photo Credit: Reuters

Across the world, many cities are slowly sinking. Most are on the coast, including tropical megacities like Jakarta in Indonesia or Manila in the Philippines, or places like New Orleans, Vancouver or much of the Netherlands. Other sinking cities, like Mexico City and many of those in China, can be well inland. Yet this still remains a widely overlooked hazard.

In my three decades assessing this topic, I have reviewed evidence of subsidence in cities around the world. The problem is especially significant in Asia, where about 60% of the world’s population lives and the cities are growing rapidly. However, some cities have also shown there are things that can be done to stop subsidence.

The problem is illustrated by a recent study by researchers in China which found that more than a third of the country’s urban population – some 270 million people – live in sinking cities.

The authors analysed satellite-derived data from 2015 to 2022 across China’s 82 most important cities to produce accurate and consistent maps of vertical land movement. Consistently measuring subsidence in all these cities, with a collective population of nearly 700 million people, is a great achievement.

They found 37 of the 82 cities they looked at were sinking, and nearly 70 million people are experiencing rapid subsidence of 10mm a year or more. This may not sound much but the subsidence accumulates over time and can damage infrastructure and buildings, and make floods more dangerous.

There are a number of sinking hotspots in China mainly in the east of the country, especially near the coast. These include the inland capital Beijing and the nearby (London-sized) port city of Tianjin.

Why cities sink

The subsidence has multiple causes, both natural and human-induced. Most large changes are human-induced. For cities built on geologically young sediments such as river deltas and floodplains, the biggest cause of subsidence is people withdrawing or draining water found underground.

This groundwater is safer to drink than surface water, so as a city grows it tends to extract even more water from below. This causes the soil to consolidate and the surface above to lower.

Other causes of city sinking include mines below some cities slowly collapsing, or land reclamations which are widespread along China’s coast. The weight of the fill used to reclaim new land from the sea can cause the land to sink.

Cities often sink unevenly, and this differential subsidence is a much greater challenge than when an entire city sinks at a uniform rate. For instance traffic vibration and tunnelling is also a contributing factor in certain areas – the new study found that Beijing is sinking much faster near subways and highways, up to 45mm a year.

Subsidence is often attributed to the weight of buildings, but this is probably overstated as modern foundation design aims to minimise the effect to avoid building damage.

Coastal cities such as Tianjin are especially affected as sinking land reinforces the problem of climate change-driven sea-level rise. The sinking of sea defences is one reason why Hurricane Katrina devastated New Orleans in 2005.

China’s biggest city Shanghai has subsided up to three metres over the last 100 years. Built on already low-lying land where the Yangtze Delta meets the ocean, much of the city is barely above sea level, greatly increasing the consequences if flooding occurs.

The authors of the new study combined rates of subsidence with projected sea-level rise to estimate that the urban area in China below sea level could triple in size by 2120, affecting between 55 million and 128 million residents. This could be catastrophic without massive adaptation.

How to stop sinking

Parts of Japan’s two largest cities, Tokyo and Osaka, sank by several metres during the 20th century. However, in the 1960s and 70s both banned groundwater withdrawal and provided alternative surface water supplies. This in turn stopped or greatly reduced city subsidence – the strategy had been effective.

Shanghai in China followed a similar strategy a decade or so later. The latest study noted the city today has relatively moderate subsidence compared to the hotspot of Tianjin. The Chinese government already aspires to mitigate human-induced subsidence, and this new study shows all the cities where this needs to be considered.

But if cities are unable to stop or control sinking then they have to adapt to the reality, especially in coastal areas. In China’s low-lying coastal areas, dikes are almost universal. But a combination of sinking land and rising seas means they are already being raised.

As illustrated by the new China study, satellites are delivering unprecedented subsidence data in time and space. They provide consistent measurements across China (and potentially the world) and overcome concerns about sinking equipment which make subsidence so difficult to measure on the ground.

These satellite measurements can be repeated regularly to identify trends, and provide an important step on the road towards a solution to sinking cities. As someone who started their career when ground surveying was the norm, this is all very exciting.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The world just experienced its hottest April on record. File (Image used for representation purpose only)
| Photo Credit: Reuters

The world just experienced its hottest April on record, extending an 11-month streak in which every month set a temperature record, the European Union’s climate change monitoring service said on May 8.

Each month since June 2023 has ranked as the planet’s hottest on record, compared with the corresponding month in previous years, the Copernicus Climate Change Service (C3S) said in a monthly bulletin.

Including April, the world’s average temperature was the highest on record for a 12-month period – 1.61 degrees Celsius above the average in the 1850-1900 pre-industrial period.

Some of the extremes — including months of record breaking sea surface temperatures — have led scientists to investigate whether human activity has now triggered a tipping point in the climate system.

“I think many scientists have asked the question whether there could be a shift in the climate system,” said Julien Nicolas, C3S Senior Climate Scientist.

Greenhouse gas emissions from burning fossil fuels are the main cause of climate change. In recent months, the natural El Nino phenomenon, which warms the surface waters in the eastern Pacific Ocean, has also raised temperatures.

Scientists have already confirmed that climate change caused some specific weather extremes in April, including a heatwave in the Sahel linked to potentially thousands of deaths.

Ms. Hayley Fowler, a climate scientist at Newcastle University, said the data showed the world is perilously close to breaching the 2015 Paris Agreement’s goal to cap global warming at 1.5 degree Celsius.

“At what point do we declare we’ve lost the battle to keep temperatures below 1.5°C? My personal opinion is we’ve already lost that battle, and we really need to think very seriously about keeping below 2°C and reducing our emissions as fast as we can,” she said.

Countries agreed the 1.5°C goal at a U.N. climate summit in 2015. It is the level scientists say would avoid the most disastrous consequences of warming, like fatal heat, flooding and the irreversible loss of ecosystems.

Technically, the 1.5°C target has not yet been missed, as it refers to an average global temperature over decades. But some scientists have said the goal can no longer realistically be met, and have urged Governments to cut CO2 emissions faster to limit overshoot of the target.

C3S’ dataset goes back to 1940, which the scientists cross-checked with other data to confirm that last month was the hottest April since the pre-industrial period.

Pfizer’s gene therapy trial for Duchenne muscular dystrophy resulted in a young patient’s death. File
| Photo Credit: Reuters

A young patient died due to cardiac arrest after receiving Pfizer’s experimental gene therapy being tested in a mid-stage trial for a muscle-wasting disorder called Duchenne muscular dystrophy(DMD), the drugmaker told Reuters on May 7.

“A fatal serious adverse event was reported as cardiac arrest for a participant in the Phase 2 DAYLIGHT study,” a company spokesperson told Reuters in an emailed response.

The trial is testing boys two to three years of age with Duchenne muscular dystrophy (DMD), a genetic muscle wasting disorder in which most patients lack the protein dystrophin which keeps muscles intact. The disorder affects an estimated one-in-3,500 male births worldwide.

“The patient received the investigational gene therapy, fordadistrogene movaparvovec, in early 2023,” as per a statement from a community letter attributed to the drugmaker’s DMD gene therapy team and posted by a nonprofit advocacy group.

Pfizer did not immediately respond to a Reuters request seeking confirmation on the community letter attributed to the company.

All participants will be followed in the study, for five years after treatment with gene therapy, initiated in August 2022 and estimated to complete in early 2029, as per information updated by the company on a registry of clinical trials.

The company said, together with the independent external data monitoring committee, it is in the process of reviewing the data to understand the potential cause.

The gene therapy candidate is also being tested in the another late-stage DMD study, called CIFFREO, in patients in boys 4 to less than 8 years of age, as per pipeline updates on the drugmaker’s website.

There is not an impact to our expectation of having late-stage results, the company told Reuters in its email.

“We anticipate potentially beginning the primary analysis of the Phase 3 CIFFREO trial of fordadistrogene movaparvovec at the end of this month and sharing top-line results relatively soon,” it added.

A critical NASA mission in the search for life beyond Earth, Mars Sample Return, is in trouble. Its budget has ballooned from US$5 billion to over $11 billion, and the sample return date may slip from the end of this decade to 2040.

The mission would be the first to try to return rock samples from Mars to Earth so scientists can analyze them for signs of past life.

NASA Administrator Bill Nelson said during a press conference on April 15, 2024, that the mission as currently conceived is too expensive and too slow. NASA gave private companies a month to submit proposals for bringing the samples back in a quicker and more affordable way.

As an astronomer who studies cosmology and has written a book about early missions to Mars, I’ve been watching the sample return saga play out. Mars is the nearest and best place to search for life beyond Earth, and if this ambitious NASA mission unraveled, scientists would lose their chance to learn much more about the red planet.

The habitability of Mars

The first NASA missions to reach the surface of Mars in 1976 revealed the planet as a frigid desert, uninhabitable without a thick atmosphere to shield life from the Sun’s ultraviolet radiation. But studies conducted over the past decade suggest that the planet may have been much warmer and wetter several billion years ago.

The Curiosity and Perseverance rovers have each shown that the planet’s early environment was suitable for microbial life.

They found the chemical building blocks of life and signs of surface water in the distant past. Curiosity, which landed on Mars in 2012, is still active; its twin, Perseverance, which landed on Mars in 2021, will play a crucial role in the sample return mission.

Why astronomers want Mars samples

The first time NASA looked for life in a Mars rock was in 1996. Scientists claimed they had discovered microscopic fossils of bacteria in the Martian meteorite ALH84001. This meteorite is a piece of Mars that landed in Antarctica 13,000 years ago and was recovered in 1984. Scientists disagreed over whether the meteorite really had ever harbored biology, and today most scientists agree that there’s not enough evidence to say that the rock contains fossils.

Several hundred Martian meteorites have been found on Earth in the past 40 years. They’re free samples that fell to Earth, so while it might seem intuitive to study them, scientists can’t tell where on Mars these meteorites originated. Also, they were blasted off the planet’s surface by impacts, and those violent events could have easily destroyed or altered subtle evidence of life in the rock.

There’s no substitute for bringing back samples from a region known to have been hospitable to life in the past. As a result, the agency is facing a price tag of $700 million per ounce, making these samples the most expensive material ever gathered.

A compelling and complex mission

Bringing Mars rocks back to Earth is the most challenging mission NASA has ever attempted, and the first stage has already started.

Perseverance has collected over two dozen rock and soil samples, depositing them on the floor of the Jezero Crater, a region that was probably once flooded with water and could have harbored life. The rover inserts the samples in containers the size of test tubes. Once the rover fills all the sample tubes, it will gather them and bring them to the spot where NASA’s Sample Retrieval Lander will land. The Sample Retrieval Lander includes a rocket to get the samples into orbit around Mars.

The European Space Agency has designed an Earth Return Orbiter, which will rendezvous with the rocket in orbit and capture the basketball-sized sample container. The samples will then be automatically sealed into a biocontainment system and transferred to an Earth entry capsule, which is part of the Earth Return Orbiter. After the long trip home, the entry capsule will parachute to the Earth’s surface.

The complex choreography of this mission, which involves a rover, a lander, a rocket, an orbiter and the coordination of two space agencies, is unprecedented. It’s the culprit behind the ballooning budget and the lengthy timeline.

Sample return breaks the bank

Mars Sample Return has blown a hole in NASA’s budget, which threatens other missions that need funding.

The NASA center behind the mission, the Jet Propulsion Laboratory, just laid off over 500 employees. It’s likely that Mars Sample Return’s budget partly caused the layoffs, but they also came down to the Jet Propulsion Laboratory having an overfull plate of planetary missions and suffering budget cuts.

Within the past year, an independent review board report and a report from the NASA Office of Inspector General raised deep concerns about the viability of the sample return mission. These reports described the mission’s design as overly complex and noted issues such as inflation, supply chain problems and unrealistic costs and schedule estimates.

NASA is also feeling the heat from Congress. For fiscal year 2024, the Senate Appropriations Committee cut NASA’s planetary science budget by over half a billion dollars. If NASA can’t keep a lid on the costs, the mission might even get canceled.

Thinking out of the box

Faced with these challenges, NASA has put out a call for innovative designs from private industry, with a goal of shrinking the mission’s cost and complexity. Proposals are due by May 17, which is an extremely tight timeline for such a challenging design effort. And it’ll be hard for private companies to improve on the plan that experts at the Jet Propulsion Laboratory had over a decade to put together.

An important potential player in this situation is the commercial space company SpaceX. NASA is already partnering with SpaceX on America’s return to the Moon. For the Artemis III mission, SpaceX will attempt to land humans on the Moon for the first time in more than 50 years.

However, the massive Starship rocket that SpaceX will use for Artemis has had only three test flights and needs a lot more development before NASA will trust it with a human cargo.

In principle, a Starship rocket could bring back a large payload of Mars rocks in a single two-year mission and at far lower cost. But Starship comes with great risks and uncertainties. It’s not clear whether that rocket could return the samples that Perseverance has already gathered.

Starship uses a launchpad, and it would need to be refueled for a return journey. But there’s no launchpad or fueling station at the Jezero Crater. Starship is designed to carry people, but if astronauts go to Mars to collect the samples, SpaceX will need a Starship rocket that’s even bigger than the one it has tested so far.

Sending astronauts also carries extra risk and cost, and a strategy of using people might end up more complicated than NASA’s current plan.

With all these pressures and constraints, NASA has chosen to see whether the private sector can come up with a winning solution. We’ll know the answer next month.

Chris Impey, University Distinguished Professor of Astronomy, University of Arizona

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Flowering plants – from corn, wheat, rice and potatoes to maple, oak, apple and cherry trees as well as roses, tulips, daisies and dandelions and even the corpse flower and voodoo lily – are cornerstones of Earth’s ecosystems and essential for humankind.
| Photo Credit: Reuters

Flowering plants – from corn, wheat, rice and potatoes to maple, oak, apple and cherry trees as well as roses, tulips, daisies and dandelions and even the corpse flower and voodoo lily – are cornerstones of Earth’s ecosystems and essential for humankind.

New research based on genome data for 9,506 species, as well as an examination of 200 fossils, provides the deepest understanding to date of the evolutionary history of flowering plants, called angiosperms – the largest and most diverse plant group. It details how angiosperms appeared and became dominant during the age of dinosaurs and how they have changed over time.

The scientists devised a new tree of life for angiosperms, covering 15 times more types of flowering plants – nearly 60% of them – than the nearest comparable study.

“It is a massive leap forward in our understanding of plant evolution,” said botanist William Baker of the Royal Botanic Gardens, Kew (RBG Kew) in London, senior author of the research published on Wednesday in the journal Nature.

Angiosperms, plants that produce flowers and generate their seeds in fruits, encompass about 330,000 species and comprise about 80% of the world’s plants. They include, among others, all the major food crops, grasses, most broad-leaved trees and most aquatic plants. Their closest relatives are the gymnosperms, a group that preceded them on Earth and includes conifers and some others, with a bit more than 1,000 species.

The study identified two pulses of diversification among angiosperms. The first one occurred around 150-140 million years ago at the dawn of their existence during the Mesozoic era, with 80% of major angiosperm lineages arising during that time. The next one happened about 100 million years later during the Cenozoic era, after the demise of the dinosaurs and the rise of mammals, amid decreasing global temperatures.

“Angiosperms have many structural adaptations that confer advantages over gymnosperms, but chief among these are those contributing to reproductive success,” Baker said.

Gymnosperms and angiosperms both have seeds, but the flowering plants have enclosed seeds that protect them from dehydration and enable them to prosper in a wider range of environments, from tropics to deserts to Antarctica.

They also evolved the flower, a structure that allowed them to form relationships with animal pollinators, especially insects, while gymnosperms usually rely upon the wind for pollination. Angiosperms evolved a high diversity of fruit types, permitting effective seed dispersal.

“With these innovations, angiosperms have become invincible,” Baker said.

Charles Darwin, the 19th century British naturalist and architect of evolutionary theory, was astonished by how flowering plants exploded onto the scene in the Mesozoic fossil record.

In an 1879 letter to Joseph Hooker, RBG Kew’s then-director, Darwin wrote that “the rapid development as far as we can judge of all the higher plants within recent geological times is an abominable mystery.”

“Remarkably,” Baker said, “we have been able to use the ‘molecular fossil record,’ the accumulated change in DNA over time, to see real evidence of that explosion happening at the dawn of the angiosperms.”

Flowering plants provide the majority of calories consumed by humans – grains, fruits and vegetables – including indirectly as feed for livestock. They also have enthralled people with their beauty – fields of sunflowers, bouquets of roses, bunches of calla lilies – and their pleasant fragrance.

“They are sources of many of our medicines and hold potential solutions to global challenges, such as climate change, biodiversity loss, human health, food security and renewable energy,” Baker said.

The study could help scientists better understand disease and pest resistance in angiosperms and navigate potential new medicinal uses – for example, to combat malaria.

“Combining the tree of life with extinction risk assessments for each lineage allow us to prioritize lineages for conservation based on their uniqueness,” RBG Kew botanist and study lead author Alexandre Zuntini said. “This is extremely important for mankind, as these lineages may hold chemical compounds or even genes that can be useful for survival of our species.”

An artist’s impression of a type of neutron star called a magnetar. Magnetars are the cosmic objects with the strongest magnetic fields ever measured in the universe.
| Photo Credit: Reuters

Magnetars are among the universe’s most extreme objects – a class of the compact stellar remnants called neutron stars that possess immensely strong magnetic fields. Once in a while, they produce enormous eruptions of gamma rays in the strongest nondestructive release of energy known in the cosmos.

Scientists have now detected the most distant-known instance of one of these eruptions, called a giant flare, from a magnetar residing in a galaxy called Messier 82, or M82. This surge of gamma rays, the most energetic form of light, unleashed in just a tenth of a second the amount of energy our sun would emit in a span of roughly 10,000 years, they said.

Only two confirmed giant flares have been observed in our Milky Way galaxy, in 2004 and 1998, and only one previous one in another galaxy, in 1979 in the Milky Way’s neighboring Large Magellanic Cloud, the researchers said.

“Giant flares are very rare events,” said astrophysicist Sandro Mereghetti of Italy’s National Institute for Astrophysics (INAF) in Milan, lead author of the research published on Wednesday in the journal Nature. “The Milky Way contains at least 30 magnetars, possibly many more, which have not been seen to emit giant flares.”

M82, nicknamed the “cigar galaxy” because when viewed edge-on it has an elongated and cigar-like shape, is 12 million light-years from Earth in the constellation Ursa Major. A light year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km). The magnetar giant flare from the Large Magellanic Cloud was about 160,000 light-years from Earth.

The M82 giant flare was the most distant known but not the most energetic. The one spotted in 2004 had the energy equivalent to about a million years of output from the sun.

While there are more energetic cosmic events such as supernova explosions at the end of a massive star’s life and gamma-ray bursts caused by two neutron stars merging, those involve destruction, unlike giant flares. Magnetars also emit occasional surges of gamma rays and X-rays at lower energy levels than giant flares.

Neutron stars are born in the explosion and collapse of stars eight to 25 times the mass of the sun at the end of their life cycle. They compress one or two times the sun’s mass into a sphere only the size of a city.

“They are the most compact and dense astrophysical objects. They are as dense as atomic nuclei,” INAF astrophysicist and study co-author Michela Rigoselli said of neutron stars.

The main trait that sets magnetars apart from other neutron stars is a magnetic field 1,000 to 10,000 times stronger than an ordinary neutron star’s magnetism and a trillion times that of the sun.

“We can say that magnetars are neutron stars powered by their own magnetic energy. This does not happen in ordinary neutron stars,” Mereghetti said.

“A giant flare originates from a reconfiguration and a reconnection of the magnetic field of the magnetar,” Rigoselli added.

The magnetar in this research is believed to spin rapidly, perhaps completing a rotation every few seconds. Its giant flare was detected by the European Space Agency’s Integral space observatory on Nov. 15, 2023, in M82, a galaxy boasting a star formation rate much higher than the Milky Way’s – called a “starburst galaxy.”

“The fact that Messier 82 is so active in star formation is relevant for our finding,” Rigoselli said. “In such an active galaxy, there are many young, massive stars like those which evolve into supernova explosions and give birth to neutron stars. It would have been suspicious to detect a magnetar giant flare coming from a quiescent galaxy.”