Two years ago, 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 say they’ve confirmed the presence of that lake — and found three more.
The discovery, reported on 28 September in Nature Astronomy1, was made using radar data from the European Space Agency’s (ESA) orbiting Mars Express spacecraft. 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 between 2012 and 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 three smaller lakes, each a few kilometres wide.
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 may 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 about five times that of seawater can support life, but as you approach 20 times that of seawater life is no longer present, says John Priscu, an environmental scientist at Montana State University.
“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].”
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 yet convinced that the regions identified 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 from Purdue University, in West Lafayette, Indiana.
Jack Holt, a planetarty scientist at the University of Arizonasays that while 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 (MRO). “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.
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.”
An unusual meteorite that streaked across the sky of Michigan as a fireball before landing on a frozen lake in 2018 has granted scientists with a peek at the things space rocks can ferry down to Earth.
Namely, the meteorite was chock full of organic compounds — carbon-containing molecules that serve as the building blocks of life on Earth — that had clear extraterrestrial origins, according to research accepted for publication in the journal Meteoritics & Planetary Science. In this case, scientists from Chicago’s Field Museum of Natural History got to it so quickly that they were able to rule out the sorts of contamination that usually impedes meteorite research.
Typically meteorites are teeming with life, but only because they were sitting around long enough for Earthly microbes or lichens to move in and colonize them, lead study author Philipp Heck, a Field Museum curator and University of Chicago professor, explained in a press release.
“This meteorite is special because it fell onto a frozen lake and was recovered quickly,” Heck said. “It was very pristine. We could see the minerals weren’t much altered and later found that it contained a rich inventory of extraterrestrial organic compounds.”
It’s compounds like these that some scientists theorize kickstarted life on Earth after they were brought down by a series of ancient meteorite impacts.
“These kinds of organic compounds were likely delivered to the early Earth by meteorites and might have contributed to the ingredients of life,” Heck said in the release.
Halloween Predictions: Much of British Columbia is eerily cold under a full moon
While the weather is expected to be frighteningly cold in most parts of BC this Halloween, those who venture outside might be in for a place to have fun.
A rare full “blue” moon is expected Saturday night, and it is the second full moon this month.
The last time Trick-or-Treaters went out under a full moon in British Columbia was in 2001, but the last Halloween moon in all time zones was in 1944, according to a farmers’ calendar.
As for the weather, if you’re in Metro Vancouver, it will likely be clear and sunny during the day with temperatures as low as 11 degrees Celsius, then partly cloudy at night with temperatures as low as 5 degrees Celsius, according to the Canadian Department of Environment and Climate Change.
Elsewhere in British Columbia, areas of Prince George and Williams Lake should see a combination of sun and cloud with highs of 4 or 5 ° C and an overnight low of 2 ° C, while in the Okanagan it is likely overcast and 10 ° C low. Down to 4 degrees Celsius throughout the night with the chance of light showers.
In the northern region of Dis Lake, the weather appears sunny during the day and freezing at night, with the temperature dropping to minus 7 degrees Celsius throughout the night.
In central British Columbia, it may snow in some communities on Saturday. The agency expects a good chance of flash waves in Smithers during the day, but it will fall throughout the night.
While the weather is expected to be frightfully cold in much of B.C. this Halloween, those who venture outdoors may be in for a treat.
A rare full “blue” moon is expected Saturday night, the second full moon this month.
The last time trick-or-treaters went out under a full moon in B.C. was in 2001, but the last Halloween full moon in all time zones was in 1944, according to the Farmer’s Almanac.
As for the weather, if you’re in Metro Vancouver it’s likely going to be clear and sunny during the day with a high of 11 C, and then partly cloudy at night with a low of 5 C, according to Environment and Climate Change Canada.
Elsewhere in B.C., the Prince George and Williams Lake areas should see a mix of sun and cloud with a high of around 4 or 5 C and an overnight low of 2 C, while in the Okanagan it will likely be overcast and 10 C, dipping down to 4 C overnight with a slight chance of showers.
In the northern region of Dease Lake, the forecast looks for sunny during the day and freezing at night, plunging to minus 7 C overnight.
In the central B.C. region, some communities may have snow Saturday. The agency is forecasting a good chance of flurries in Smithers during the day but showers overnight.
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