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Arctic ice melt doesn't boost sea levels, so do we care? – FRANCE 24

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Paris (AFP)

US government scientists reported Monday that the Arctic Ocean’s floating ice cover has shrivelled to its second lowest extent since satellite records began in 1979.

Until this month, only once in the last 42 years has Earth’s frozen skull cap covered less than four million square kilometres (1.5 million square miles).

The trend line is clear: sea ice extent has diminished 14 percent per decade over that period. The Arctic could see it’s first ice-free summer as early as 2035, researchers reported in Nature Climate Change last month.

But all that melting ice and snow does not directly boost sea levels any more than melted ice cubes make a glass of water overflow, which gives rise to an awkward question: who cares?

Granted, this would be bad news for polar bears, which are already on a glide path towards extinction, according to a recent study.

And yes, it would certainly mean a profound shift in the region’s marine ecosystems, from phytoplankton to whales.

But if our bottom-line concern is the impact on humanity, one might legitimately ask, “So what?”.

As it turns out, there are several reasons to be worried about the knock-on consequences of dwindling Arctic sea ice.

– Feedback loops –

Perhaps the most basic point to make, scientists say, is that a shrinking ice cap is not just a symptom of global warming, but a driver as well.

“Sea ice removal exposes dark ocean, which creates a powerful feedback mechanism,” Marco Tedesco, a geophysicist at Columbia University’s Earth Institute, told AFP.

Freshly fallen snow reflects 80 percent of the Sun’s radiative force back into space.

But when that mirror-like surface is replaced by deep blue water, about the same percentage of Earth-heating energy is absorbed instead.

And we’re not talking about a postage stamp area here: the difference between the average ice cap minimum from 1979 to 1990 and the low point reported today — more than 3 million km2 — is twice the size of France, Germany and Spain combined.

The oceans have already soaked up 90 percent of the excess heat generated by manmade greenhouse gases, but at a terrible cost, including altered chemistry, massive marine heatwaves and dying coral reefs.

And at some point, scientists warn, that liquid heat sponge may simply become saturated.

– Altering ocean currents –

Earth’s complex climate system includes interlocking ocean currents driven by wind, tides and something called the thermohaline circulation, which is itself powered by changes in temperature (“thermo”) and salt concentration (“haline”).

Even small changes in this Great Ocean Conveyor Belt — which moves between poles and across all three major oceans — can have devastating climate impacts.

Nearly 13,000 years ago, for example, as Earth was transitioning out of an ice age into the interglacial period that allowed our species to thrive, global temperatures abruptly plunged several degrees Celsius. They jumped back up again about 1,000 years later.

Geological evidence suggests a slowdown in the thermohaline circulation caused by a massive and rapid influx of cold, fresh water from the Artic region was partly to blame.

“The fresh water from melting sea ice and grounded ice in Greenland perturbs and weakens the Gulf Stream,” part of the conveyor belt flowing in the Atlantic, said Xavier Fettweis, a research associate at the University of Liege in Belgium.

“This is what allows western Europe to have a temperate climate compared to the same latitude in North America.”

The massive ice sheet atop Greenland’s land mass saw a net loss of more than half-a-trillion tonnes last year, all of it flowing into the sea.

Unlike sea ice, which doesn’t increase sea levels when it melts, runoff from Greenland does.

That record amount was due in part to warmer air temperatures, which have risen twice as fast in the Arctic as for the planet as a whole.

But it was also caused by a change in weather patterns, notably an increase in sunny summer days.

“Some studies suggest that this increase in anticyclonic conditions in the Arctic in summer results in part from the minimum sea ice extent,” Fettweis told AFP.

– Bears on thin ice –

The current trajectory of climate change and the advent of ice-free summers — defined by the UN’s IPCC climate science panel as under one million km2 — would indeed starve polar bears into extinction by century’s end, according to a July study in Nature.

“Human-caused global warming means that polar bears have less and less sea ice to hunt on in the summer months,” Steven Amstrup, lead author of the study and chief scientist of Polar Bears International, told AFP.

“The ultimate trajectory of polar bears with unabated greenhouse gas emissions is disappearance.”

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Trio returns to Earth after 6 months aboard International Space Station – CBC.ca

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A trio of space travellers safely returned to Earth on Thursday after a six-month mission on the International Space Station.

The Soyuz MS-16 capsule carrying NASA astronaut Chris Cassidy, and Roscosmos’ Anatoly Ivanishin and Ivan Vagner landed on the steppes of Kazakhstan southeast of the town of Dzhezkazgan at 7:54 a.m. local time Thursday. After a brief medical checkup, the three will be taken by helicopters to Dzhezkazgan from where they will depart home.

The crew smiled as they talked to masked members of the recovery team, and NASA and Roscosmos reported that they were in good condition.

As part of additional precautions due to the coronavirus, the rescue team members meeting the crew were tested for the virus and the number of people involved in the recovery effort was limited.

Cassidy, Ivanishin and Vagner spent 196 days in orbit since arriving at the station on April 9.

NASA’s Kate Rubins and Roscosmos’ Sergey Ryzhikov and Sergey Kud-Sverchkov arrived at the orbiting outpost a week ago for a six-month stay.

Before the crew’s departure, Russian cosmonauts were able to temporarily seal the air leak they tried to locate for several months. The small leak has posed no immediate danger to the station’s crew, and Roscosmos engineers have been working on a permanent seal.

In November, Rubins, Ryzhikov and Kud-Sverchkov are expected to greet NASA’s SpaceX first operational Crew Dragon mission comprising NASA astronauts Mike Hopkins, Victor Glover and Shannon Walker, and Japan Aerospace Exploration Agency astronaut Soichi Noguchi. It follows a successful Demo-2 mission earlier this year.

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Osiris-Rex: Nasa asteroid mission confident of success – BBC News

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Osiris-Rex: Nasa asteroid mission confident of success

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By Jonathan Amos
BBC Science Correspondent

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.css-14iz86j-BoldTextfont-weight:bold;“We really did kind of make a mess.”

That was Dante Lauretta’s take after reviewing the first pictures to come down from .css-yidnqd-InlineLink:linkcolor:#3F3F42;.css-yidnqd-InlineLink:visitedcolor:#696969;.css-yidnqd-InlineLink:link,.css-yidnqd-InlineLink:visitedfont-weight:bolder;border-bottom:1px solid #BABABA;-webkit-text-decoration:none;text-decoration:none;.css-yidnqd-InlineLink:link:hover,.css-yidnqd-InlineLink:visited:hover,.css-yidnqd-InlineLink:link:focus,.css-yidnqd-InlineLink:visited:focusborder-bottom-color:currentcolor;border-bottom-width:2px;color:#B80000;@supports (text-underline-offset:0.25em).css-yidnqd-InlineLink:link,.css-yidnqd-InlineLink:visitedborder-bottom:none;-webkit-text-decoration:underline #BABABA;text-decoration:underline #BABABA;-webkit-text-decoration-thickness:1px;text-decoration-thickness:1px;-webkit-text-decoration-skip-ink:none;text-decoration-skip-ink:none;text-underline-offset:0.25em;.css-yidnqd-InlineLink:link:hover,.css-yidnqd-InlineLink:visited:hover,.css-yidnqd-InlineLink:link:focus,.css-yidnqd-InlineLink:visited:focus-webkit-text-decoration-color:currentcolor;text-decoration-color:currentcolor;-webkit-text-decoration-thickness:2px;text-decoration-thickness:2px;color:#B80000;Nasa’s Osiris-Rex probe following its bid to grab a sample from asteroid Bennu on Tuesday.

Dust and grit flew in all directions but that was good news, enthused the University of Arizona professor.

“Everything that we can see from these initial images indicates sampling success. So in case you can’t tell, I’m pretty excited.”

The principal investigator’s team now has to work out precisely how much material Osiris-Rex might have lifted from the surface of 500m-wide Bennu.

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If it’s a kilo or more, it would represent the biggest extra-terrestrial sample cache since the Apollo astronauts gathered rocks from the Moon some 50 years ago.

But even a smaller amount would still be a great prize.

Bennu is a very primitive object, with chemistry preserved from the dawn of the Solar System more than 4.5 billion years ago. As such, it can tell us a great deal about how the Sun and the planets came into being.

Osiris-Rex used what had been described as a “reverse vacuum cleaner” to acquire its clutch of “soil”.

More properly called the Touch-and-Go Sample Acquisition Mechanism, or Tag-Sam, this device comprised a long boom with a ring-shaped collection chamber on the end.

The idea was to deliver a squirt of nitrogen when the Tag-Sam made contact with the asteroid.

The hope was this gas would stir up Bennu’s fragmented surface, leading to a considerable number of rocky pieces getting trapped inside the collection chamber.

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The downlinked pictures certainly suggested the strategy was the right one.

Osiris-Rex may have been in contact with Bennu for only six seconds before retreating, but the sampling ring was flat and stable, and even pressing into the soil slightly. This should have maximised the chances of retaining material.

Rich Burns, Nasa’s project manager on the mission, lauded the the way his team managed to put the probe in just the right place on Bennu – almost exactly at the centre of the targeted sampling zone.

“We’re over 320 million km away from Earth at this point, and we touched this asteroid within a metre of where we intended to. So that’s extraordinary and a real credit to our team,” he told reporters.

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Artwork of probe

image copyrightNASA/Goddard/UoA

On Thursday, engineers will command the spacecraft to take detailed pictures of the sampling ring to try to see what it contains.

And then on Saturday, they’ll make Osiris-Rex spin itself around with the Tag-Sam outstretched. Any extra mass on board will change the level of torque required to turn the probe, compared with the level that was needed to perform the same rotation exercise prior to sample acquisition.

“We are expecting a final sample mass measurement report on Monday,” explained Sandy Freund, the mission operations manager at Lockheed Martin, the company that manufactured Osiris-Rex.

It seems highly likely that Osiris-Rex has achieved its objective of taking at least 60g off Bennu. But if it hasn’t, there are two more nitrogen bottles still aboard the probe to facilitate further sampling bids. And there’s plenty of time, too.

The spacecraft is not scheduled to depart Bennu for Earth until April next year. A landing on Earth for any rock cache in this timeline would be late 2023.

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Prof Lauretta once again on Wednesday’s paid tribute to the British scientist who conceived Osiris-Rex.

This was Bristol-born Michael Drake who held senior science positions at the University of Arizona in Tucson.

He worked up the concept for the mission but sadly died in 2011, aged 65, just months after Nasa had green-lit the project.

“I’m pleased to see that my dad’s legacy is being honoured at this exciting time in Osiris-Rex’s mission,” Michael Drake’s son, Matt Drake, told BBC News.

“My father’s idea to study near-Earth asteroids as a means of peering back in time to the birth of the Solar System finally came to fruition during [Tuesday’s] Tag event.

“As the principal investigator of this team from its inception until his passing almost 10 years later, he would have been incredibly proud of his team’s accomplishments.”

Osiris-Rex carries a plaque of remembrance to Michael Drake.

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Michael Drake

image copyrightUoA

Bennu size comparison with Empire State Building

Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos

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Rare 'blue moon' to appear on Halloween this year – Richmond News

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The year 2020 has brought many surprises and this year’s Halloween is no different.

A rare “blue full moon” will be appearing on Halloween night this year.

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While the moon will not look blue, the term “blue moon” is given when two full moons appear in a single month.

A full moon on Halloween occurs roughly once every 19 years – a pattern known as the Metonic Cycle.

According to the Old Farmer’s Almanc, the cycle is uncommon and happens on average every two and a half to three years with the last time two full moons appearing in the same month in 2018.

The next illuminated Halloween full moon, says astronomers, after 2020 will be in the 2039, 2058, 2077 and 2096.

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