Water on Mars in 2020.

January 04th, 2021 (Nature Science). Two years ago (DATE Sep 28th, 2020), planetary scientists reported the discovery of a large saltwater lake under the ice at Mars’s south pole, a finding that was met with excitement and some scepticism. Now, researchers have confirmed the presence of that lake and found three more.

The discovery, reported on 28 September in Nature Astronomy, was made using radar data from the European Space Agency’s Mars-orbiting spacecraft, called Mars Express. It follows the detection of a single subsurface lake in the same region in 2018 which, if confirmed, would be the first body of liquid water ever detected on the red planet and a possible habitat for life. But that finding was based on just 29 observations made from 2012 to 2015, and many researchers said they needed more evidence to support the claim. The latest study used a broader data set comprising 134 observations from 2012 to 2019.

“We identified the same body of water, but we also found three other bodies of water around the main one,” says planetary scientist Elena Pettinelli at the University of Rome, who is one of the paper’s co-authors. “It’s a complex system.”

The team used a radar instrument on Mars Express called the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) to probe the planet’s southern polar region. MARSIS sends out radio waves that bounce off layers of material in the planet’s surface and subsurface. The way the signal is reflected back indicates the kind of material that is present at a particular location rock, ice or water, for example. A similar method is used to identify subsurface glacial lakes on Earth. The team detected some areas of high reflectivity that they say indicate bodies of liquid water trapped under more than one kilometre of Martian ice.

The lakes are spread over about 75,000 square kilometres an area roughly one-fifth the size of Germany. The largest, central lake measures 30 kilometres across, and is surrounded by 3 smaller lakes, each a few kilometres wide.
Salty lakes

On the surface of Mars, the low pressure that results from the planet’s lack of a substantial atmosphere makes liquid water impossible. But scientists have long thought that there could be water trapped under Mars’s surface, perhaps a remnant of when the planet once had seas and lakes billions of years ago. If such reservoirs exist, they could be potential habitats for Martian life. On Earth, life is able to survive in subglacial lakes in places such as Antarctica.

But the amount of salt present could pose problems. It’s thought that any underground lakes on Mars must have a reasonably high salt content for the water to remain liquid. Although this far beneath the surface there might be a small amount of heat from the interior of Mars, this alone would not be enough to melt the ice into water. “From a thermal point of view, it has to be salty,” says Pettinelli.

Lakes with a salt content that is about 5 times that of sea-water can support life, but as the concentration approaches 20 times that of sea-water, life is no longer present, says John Priscu, an environmental scientist at Montana State University in Bozeman.

“There’s not much active life in these briny pools in Antarctica,” says Priscu, whose group studies microbiology in icy environments. “They’re just pickled. And that might be the case [on Mars].”

 
Heated debate

The presence of the Martian lakes themselves is also still debated. After the 2018 discovery, researchers raised concerns such as the lack of an adequate heat source to turn the ice into water. And, although the latest finding supports the 2018 observation and involves much more data, not everyone is convinced that the identified regions are liquid water.

“If the bright material really is liquid water, I think it’s more likely to represent some sort of slush or sludge,” says Mike Sori, a planetary geophysicist at Purdue University in West Lafayette, Indiana.

Jack Holt, a planetary scientist at the University of Arizona in Tucson, says that although he thinks the latest data are fine, he isn’t sure about the interpretation. “I do not think there are lakes,” says Holt, who is on the science team for the Mars Shallow Radar sounder (SHARAD) on NASA’s Mars Reconnaissance Orbiter. “There is not enough heat flow to support a brine here, even under the ice cap.”

 

A Chinese mission that is on its way to Mars might offer one way to check the claims. The Tianwen-1 mission will enter orbit in February 2021, and as well as deploying a rover onto the surface, the orbiter will carry a suite of scientific instruments. These include radar equipment that could be used to make similar observations. “Its capabilities are similar to MARSIS and SHARAD,” says David Flannery from the Queensland University of Technology in Brisbane, Australia.

 

For the time being, the prospect that these lakes are remnants of Mars’s wet past remains an exciting possibility. “There may have been a lot of water on Mars,” says Pettinelli. “And if there was water, there was the possibility of life.”

doi: https://doi.org/10.1038/d41586-020-02751-1


References

1.Lauro, S. E. et al. Nature Astron. https://doi.org/10.1038/s41550-020-1200-6 (2020).

  

© 2021 ALL RIGTHS RESERVED MSH WorldWide Company By Marcelo Santiago Hernández. 

Coronavirus Outbreak COVID-19.

Saturday April 04th, 2020. London, United Kingdom (Nature). More than a dozen research groups worldwide have started analysing wastewater for the new coronavirus as a way to estimate the total number of infections in a community, given that most people will not be tested. The method could also be used to detect the coronavirus if it returns to communities, say scientists. So far, researchers have found traces of the virus in the Netherlands, the United States and Sweden.

Analysing wastewater used water that goes through the drainage system to a treatment facility is one way that researchers can track infectious diseases that are excreted in urine or faeces, such as SARS-CoV-2. One treatment plant can capture wastewater from more than one million people, says Gertjan Medema, a microbiologist at KWR Water Research Institute in Nieuwegein, the Netherlands. Monitoring influent at this scale could provide better estimates for how widespread the coronavirus is than testing, because wastewater surveillance can account for those who have not been tested and have only mild or no symptoms, says Medema, who has detected SARS-CoV-2 genetic material viral RNA in several treatment plants in the Netherlands. “Health authorities are only seeing the tip of the iceberg.”

 

But to quantify the scale of infection in a population from wastewater samples, researchers say the groups will need to find out how much viral RNA is excreted in faeces, and extrapolate the number of infected people in a population from concentrations of viral RNA in wastewater samples.

Researchers will also need to ensure that they are looking at a representative sample of what is being excreted by the population and not just one snapshot in time, and that their tests can detect the virus at low levels, say scientists representing the Queensland Alliance for Environmental Health Sciences in Australia, a research centre that advises the state government on environmental-health risks. And it's important that wastewater surveillance, should it be feasible, does not take away resources from the testing of individuals, the group says. Some efforts to monitor the virus have been stalled by university and laboratory shut-downs and the limited availability of reagents to conduct tests the same ones used in clinics, which are already in short supply, says Kyle Bibby, an environmental engineer at the University of Notre Dame in Indiana. “We don't want to contribute to the global shortage,” he says.

 

 

 

Early-warning sign

Infection-control measures, such as social distancing, will probably suppress the current pandemic, but the virus could return once such measures are lifted. Routine wastewater surveillance could be used as a non invasive early warning tool to alert communities to new COVID-19 infections, says Ana Maria de Roda Husman, an infectious-disease researcher at the Netherlands National Institute for Public Health and the Environment in Bilthoven. The institute has previously monitored sewage to detect outbreaks of norovirus, antibioticresistant bacteria, poliovirus and measles.

 

 

de Roda Husman’s group detected traces of SARS-CoV-2 in wastewater at Schiphol Airport in Tilburg only four days after the Netherlands confirmed its first case of COVID-19 using clinical testing. The researchers now plan to expand sampling to the capitals of all 12 provinces in the Netherlands and 12 other sites that have not had any confirmed cases. Medema’s group found viral RNA in the city of Amersfoort before infections had been reported in the community.

Studies have also shown that SARS-CoV-2 can appear in faeces within three days of infection, which is much sooner than the time taken for people to develop symptoms severe enough for them to seek hospital care up to two weeks and get an official diagnosis, says Tamar Kohn, an environmental virologist at the Swiss Federal Institute of Technology in Lausanne. Tracking viral particles in wastewater could give public health officials a head start on deciding whether to introduce measures such as lockdowns, she says. “Seven to ten days can make a lot of difference in the severity of this outbreak.”

Earlier identification of the virus’s arrival in a community might limit the health and economic damage caused by COVID-19, especially if it comes back next year, says Bibby. Wastewater monitoring has been used for decades to assess the success of vaccination campaigns against poliovirus, says Charles Gerba, an environmental microbiologist at The University of Arizona in Tucson. The approach could also be used to measure the effectiveness of interventions such as social distancing, says Gerba, who has found traces of SARS-CoV-2 in raw sewage in Tucson.

 

© 2020 ALL RIGTHS RESERVED MSH WorldWide Company By Marcelo Santiago Hernández.