A NASA probe detected a strange radio signal in Venus’ atmosphere last year. Astronomers have figured out where it came from.

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NASA’s Parker Solar Probe snapped an up-close view of Venus when it flew by the planet in July 2020.

  • NASA’s Parker Solar Probe detected a strange radio signal while flying by Venus in July.
  • The probe flew through Venus’ upper atmosphere, where such signals naturally occur, to collect data.
  • The data show Venus’ atmosphere has thinned, a process linked to solar activity.
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During a close flyby of the planet Venus on July 11, 2020, NASA’s Parker Solar Probe detected something odd.

As it dipped just 517 miles above the Venusian surface, the probe’s instruments recorded a low-frequency radio signal – a telltale sign that Parker had skimmed through the ionosphere, a layer of the planet’s upper atmosphere.

This was the first time an instrument had been able to directly record measurements of Venus’ upper atmosphere in nearly three decades, and the data gives us a new understanding of how Venus changes in response to cyclic changes in the sun.

“I was just so excited to have new data from Venus,” Glyn Collinson, an astronomer at NASA’s Goddard Space Flight Center, said in a press release.

According to a recent study by Collinson’s team, Venus’ upper atmosphere was an order of magnitude thinner last year than it was in 1992 – the last time scientists were able to collect data from the planet’s atmosphere.

Venus’ thick, hot atmosphere makes it hard to explore

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The surface of Venus as seen on September 16, 2010.

Venus is similar to Earth in size and composition, yet crucially different: It’s a toxic, scorching hot hell-world that is likely completely inhospitable to life as we know it.

How the two planets could have developed into such radically different beasts is of profound interest to planetary scientists and astrobiologists searching for other habitable worlds in the galaxy.

Yet missions to explore Venus have been relatively few. There’s not much point sending landers; they can’t survive the planet’s 864-degree-Fahrenheit (462-degree-Celsius) surface.

Sending orbiting probes is also considered problematic due to the incredibly thick atmosphere of carbon dioxide and sulfuric acid rain clouds that make it hard to tell what’s happening on the surface.

For these reasons, Venus hasn’t been a popular target for dedicated missions in some time (Japan’s Akatsuki orbiter being the recent exception), and a lot of our recent data has come piecemeal, from instruments with other primary objectives, like the Parker Solar Probe.

As the Parker probe conducts its mission to study the sun in close detail, it’s been using Venus for gravity assist maneuvers – slingshotting around the planet to alter its velocity and trajectory. It was on one of these gravity assist flybys that the probe’s instruments recorded a radio signal.

Collinson, who has worked on other planetary missions, noted an odd familiarity that he couldn’t quite place in the shape of the signal.

“Then the next day, I woke up,” he said, “and I thought, ‘Oh my god, I know what this is!'”

It was the same kind of signal recorded by NASA’s Galileo probe when the space skimmed through the ionospheres of Jupiter’s moons. The ionosphere is a layer of atmosphere where solar radiation ionizes atoms, resulting in a charged plasma that produces low-frequency radio emission that scientists can detect.

Once the researchers realized the signal was ionospheric plasma, they were able to use the signal to calculate the density of the Venusian ionosphere, and compare that density to similar measurements taken in 1992. Fascinatingly, the ionosphere was an order of magnitude thinner in 2020 than it was in 1992.

The sun wreaks havoc on Venus

The team believes that thinning has something to do with solar cycles. Every 11 years, the sun’s magnetic poles swap places: south becomes north and north becomes south. It’s not clear what drives these cycles, but we do know that the poles switch when the magnetic field is at its weakest.

When the sun’s magnetic field is weak, there’s fewer instances of sunspots, solar flares, and coronal mass ejections – when the sun releases plasma and bits of its magnetic field into space. This period of minimal activity is aptly called the solar minimum.

Once the poles have switched, the magnetic field strengthens, and solar activity increases to a maximum before subsiding again for the next polar switch.

NASA sun video
A NASA image of the solar surface.

Measurements of Venus from Earth suggested that Venus’ ionosphere was changing in sync with the solar cycles, growing thicker at solar maximum and thinner at solar minimum. But without direct measurements, it was difficult to confirm – until the Parker probe’s recent flyby.

The 1992 measurement was taken at a time close to solar maximum; the 2020 measurement close to solar minimum. They were both consistent with the Earth-based measurements.

“When multiple missions are confirming the same result, one after the other, that gives you a lot of confidence that the thinning is real,” Robin Ramstad, an astronomer from the University of Colorado, Boulder, said in the release.

Exactly why the solar cycle has this effect on Venus’ ionosphere is unclear, but there are two leading theories.

The first is that the upper boundary of the planet’s ionosphere could be getting compressed to a lower altitude during solar minimum, which prevents atoms ionized on the day side from flowing to the night side, resulting in a thinner night side ionosphere. The second is that Venus’ ionosphere leaks into space at a faster rate during solar minimum.

Neither of these mechanisms could be ruled out by the data collected by the new Parker probe, but Collinson’s team hopes that more observations and future missions to Venus might be able to clarify what’s going on.

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Researchers in the Antarctic experience an isolated, confined, extreme environment akin to space – so their lives are ripe for study

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The International Space Station as seen by astronauts from NASA’s space shuttle Endeavour on February 19, 2010.

Space and humans are not a perfect mix. Scientists are constantly discovering new kinds of health risks associated with space, related to how factors like microgravity and cosmic radiation affect our bones and organs.

But prolonged exposure to the environment of space isn’t just a concern for our bodies. What about our minds?

The psychological effects of extreme isolation and confinement during long-term space travel and missions to other planets still represent a big unknown.

If we’re ever going to successfully travel through space and even colonize other worlds, we need to understand much more about what happens to people stuck in unforgiving places for long periods, while very, very far from home.

As it happens, there is a scientific name for these hostile habitats: isolated, confined, extreme (ICE) environments. There is even a field of research in which scientists probe the psychological impacts of living in conditions analogous to long jaunts in space.

Researchers exploring Ross Island, Antarctica.
Researchers exploring Ross Island, Antarctica.

Of all the places on Earth to run ICE experiments, one in particular stands out.

“The Antarctic is regarded as an ideal analog for space because its extreme environment is characterized by numerous stressors that mirror those present during long-duration space exploration,” a team of researchers led by psychologist Candice Alfano from the University of Houston wrote in a new study.

“In addition to small crews and limited communication during Antarctic winter months, the environment offers little sensory stimulation and extended periods of darkness and harsh weather conditions restrict outdoor activity. Evacuation is difficult if not impossible,” the study authors added.

Alfano and her team leveraged the natural hardship of Antarctica’s difficult conditions, monitoring the psychological health and development of personnel living and working at two remote Antarctic research stations during the nine-month study period.

The psychologists devised a monthly self-reporting tool called the Mental Health Checklist, designed to measure personnel’s emotional states and mental health, including positive adaptation (feelings of control and inspiration), poor self-regulation (feelings of restlessness, inattentiveness, and tiredness), and anxious apprehension (feelings of worry and obsessing over things).

The study also monitored and rated Antarctic personnel’s physical symptoms of illness, and Alfano’s team collected saliva samples to assess the personnel’s cortisol levels – a biomarker of stress.

Ultimately, the study results showed that the participants’ positive adaptations decreased over the course of their Antarctic mission, while poor self-regulation emotions increased.

“We observed significant changes in psychological functioning, but patterns of change for specific aspects of mental health differed,” Alfano said in a press release.

“The most marked alterations were observed for positive emotions such that we saw continuous declines from the start to the end of the mission, without evidence of a ‘bounce-back effect’ as participants were preparing to return home,” she added.

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Michael Lopez-Alegria works on the International Space Station in a spacesuit on February 8, 2007.

According to the researchers, much previous research in this area has focused on negative emotional states triggered by the conditions of isolated, confined, and extreme environments.

But it’s possible we’ve been missing out on another simultaneous problem. Diminishing positive feelings over long stays in difficult places appeared to be an almost universal response to the ICE conditions, whereas changes in negative emotion levels were more varied between individuals.

“Positive emotions such as satisfaction, enthusiasm, and awe are essential features for thriving in high-pressure settings,” Alfano said. “Interventions and countermeasures aimed at enhancing positive emotions may, therefore, be critical in reducing psychological risk in extreme settings.”

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I’m a doctor who was on the WHO’s COVID-19 mission to China. Here’s what we learned about the virus’ origins.

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The shuttered Huanan Seafood Wholesale Market in Wuhan, China, January 21, 2020.

As I write, I am in hotel quarantine in Sydney, after returning from Wuhan, China. There, I was the Australian representative on the international World Health Organization’s (WHO) investigation into the origins of the SARS-CoV-2 virus.

Much has been said of the politics surrounding the mission to investigate the viral origins of COVID-19. So it’s easy to forget that behind these investigations are real people.

As part of the mission, we met the man who, on December 8, 2019, was the first confirmed COVID-19 case; he’s since recovered. We met the husband of a doctor who died of COVID-19 and left behind a young child. We met the doctors who worked in the Wuhan hospitals treating those early COVID-19 cases, and learned what happened to them and their colleagues. We witnessed the impact of COVID-19 on many individuals and communities, affected so early in the pandemic, when we didn’t know much about the virus, how it spreads, how to treat COVID-19, or its impacts.

We talked to our Chinese counterparts – scientists, epidemiologists, doctors – over the four weeks the WHO mission was in China. We were in meetings with them for up to 15 hours a day, so we became colleagues, even friends. This allowed us to build respect and trust in a way you couldn’t necessarily do via Zoom or email.

This is what we learned about the origins of SARS-CoV-2.

The virus was most likely of animal origin

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A cyclist rides in front of the closed Huanan market in Wuhan, China on February 9, 2021.

It was in Wuhan, in central China, that the virus, now called SARS-CoV-2, emerged in December 2019, unleashing the greatest infectious disease outbreak since the 1918-19 influenza pandemic.

Our investigations concluded the virus was most likely of animal origin. It probably crossed over to humans from bats, via an as-yet-unknown intermediary animal, at an unknown location. Such “zoonotic” diseases have triggered pandemics before. But we are still working to confirm the exact chain of events that led to the current pandemic. Sampling of bats in Hubei province and wildlife across China has revealed no SARS-CoV-2 to date.

We visited the now-closed Wuhan wet market which, in the early days of the pandemic, was blamed as the source of the virus. Some stalls at the market sold “domesticated” wildlife products. These are animals raised for food, such as bamboo rats, civets, and ferret badgers. There is also evidence some domesticated wildlife may be susceptible to SARS-CoV-2. However, none of the animal products sampled after the market’s closure tested positive for SARS-CoV-2.

We also know not all of those first 174 early COVID-19 cases visited the market, including the man who was diagnosed in December 2019 with the earliest onset date.

However, when we visited the closed market, it’s easy to see how an infection might have spread there. When it was open, there would have been around 10,000 people visiting a day, in close proximity, with poor ventilation and drainage.

There’s also genetic evidence generated during the mission for a transmission cluster there. Viral sequences from several of the market cases were identical, suggesting a transmission cluster. However, there was some diversity in other viral sequences, implying other unknown or unsampled chains of transmission.

A summary of modelling studies of the time to the most recent common ancestor of SARS-CoV-2 sequences estimated the start of the pandemic between mid-November and early December. There are also publications suggesting SARS-CoV-2 circulation in various countries earlier than the first case in Wuhan, although these require confirmation.

The market in Wuhan, in the end, was more of an amplifying event rather than necessarily a true ground zero. So we need to look elsewhere for the viral origins.

Did frozen or refrigerated food play a role?

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A woman looks at frozen food in a supermarket in Beijing, China, August 13, 2020.

Then there was the “cold chain” hypothesis. This is the idea the virus might have originated from elsewhere via the farming, catching, processing, transporting, refrigeration, or freezing of food. Was that food ice cream, fish, wildlife meat? We don’t know. It’s unproven that this triggered the origin of the virus itself. But to what extent did it contribute to its spread? Again, we don’t know.

Several “cold chain” products present in the Wuhan market were not tested for the virus. Environmental sampling in the market showed viral surface contamination. This may indicate the introduction of SARS-CoV-2 through infected people, or contaminated animal products and “cold chain” products. Investigation of “cold chain” products and virus survival at low temperatures is still underway.

It’s extremely unlikely that the virus escaped from a lab

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The Wuhan Institute of Virology, pictured on April 17, 2020.

The most politically sensitive option we looked at was the virus escaping from a laboratory. We concluded this was extremely unlikely.

We visited the Wuhan Institute of Virology, which is an impressive research facility, and looks to be run well, with due regard to staff health.

We spoke to the scientists there. We heard that scientists’ blood samples, which are routinely taken and stored, were tested for signs they had been infected. No evidence of antibodies to the coronavirus was found. We looked at their biosecurity audits. No evidence.

We looked at the closest virus to SARS-CoV-2 they were working on – the virus RaTG13 – which had been detected in caves in southern China where some miners had died seven years previously.

But all the scientists had was a genetic sequence for this virus. They hadn’t managed to grow it in culture. While viruses certainly do escape from laboratories, this is rare. So, we concluded it was extremely unlikely this had happened in Wuhan.

A team of more than 30 experts 

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Members of the World Health Organization’s team investigating the origins of the coronavirus pandemic at a press conference in Wuhan, China, on February 9, 2021.

When I say “we,” the mission was a joint exercise between the WHO and the Chinese health commission. In all, there were 17 Chinese and 10 international experts, plus seven other experts and support staff from various agencies. We looked at the clinical epidemiology (how COVID-19 spread among people), the molecular epidemiology (the genetic makeup of the virus and its spread), and the role of animals and the environment.

The clinical epidemiology group alone looked at China’s records of 76,000 episodes from more than 200 institutions of anything that could have resembled COVID-19 – such as influenza-like illnesses, pneumonia, and other respiratory illnesses. They found no clear evidence of substantial circulation of COVID-19 in Wuhan during the latter part of 2019 before the first case.

What’s next?

Our mission to China was only phase one. We are due to publish our official report in the coming weeks. Investigators will also look further afield for data, to investigate evidence the virus was circulating in Europe, for instance, earlier in 2019. Investigators will continue to test wildlife and other animals in the region for signs of the virus. And we’ll continue to learn from our experiences to improve how we investigate the next pandemic.

Irrespective of the origins of the virus, individual people with the disease are at the beginning of the epidemiology data points, sequences, and numbers. The long-term physical and psychological effects – the tragedy and anxiety – will be felt in Wuhan, and elsewhere, for decades to come.

The Conversation
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