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Nasa 're-masters' classic Pale Blue Dot image of Earth – BBC News



It is unquestionably one of the greatest space images ever.

The “Pale Blue Dot” picture of Planet Earth was acquired by the Voyager 1 probe exactly 30 years ago on Friday – from a distance of about 6 billion km (4 billion miles) miles.

To mark the anniversary, the US space agency has now reprocessed this iconic view using modern techniques and software.

Nasa says the re-working has been respectful of the original.

It still shows Earth as that single, bright blue pixel in the vastness of space. And that pixel is still caught within a ray of sunlight. But the image now looks “cleaner”; the Earth is easier to pick out.

The Pale Blue Dot was part of a final sequence of frames taken by Voyager before its camera system was shut down to conserve power.

It had completed its tour of the planets and had no further use for the equipment as it headed towards interstellar space.

But Carl Sagan and Carolyn Porco, two imaging scientists on the mission, persuaded the Nasa hierarchy to make a “family portrait of the Solar System” before the power-down command was sent.

The 60 frames that Voyager returned incorporated the Sun and six of the major planets – Venus, Earth, Jupiter, Saturn, Uranus and Neptune.

Mercury and Mars (and Pluto) missed out for variety of reasons. The Red Planet, for example, couldn’t be distinguished in the streams of sunlight bouncing around inside the camera optics.

One of the reasons the photo has become so famous is because of the popularity of Sagan’s writings.

In his his 1994 book, Pale Blue Dot: A Vision of the Human Future in Space, he said: “Look again at that dot. That’s here. That’s home. That’s us.” And he went on to describe Earth as “a mote of dust suspended in a sunbeam”.

It summed up perfectly the profound “perspective” gained from the exploration of space.

Carolyn Porco, recalling the picture for the BBC in 2013, said that it gave a “crystalline, uncorrupted view of our cosmic place that erodes all delusion and confronts us with a powerful recognition of ourselves – a recognition that never fails to move us”.

Garry Hunt, the only Briton on the Voyager imaging team, says the picture is more relevant today than it’s ever been. He started his career in the Earth sciences, including climate studies, and continues to display the image in lectures.

“Every time I give a climate talk and I talk about what you’re doing now to make a change – I show this picture because it shows the Earth is an isolated speck. This tiny blue dot is the only place we can possible live, and we’re making a jolly good mess of it,” he told BBC Radio 4’s Today programme this week.

Carolyn Porco reimagined the Pale Blue Dot with the Cassini probe in 2013, turning that spacecraft’s camera system back towards Earth and capturing the blue pixel under the rings of Saturn.

Getting a view of home is now seen as something of a must-do for all far-flung missions.

The New Horizons spacecraft which made a close flyby of Pluto in 2015 and is now a little over 7 billion km from Earth is expected at some point to try to repeat Voyager’s photographic feat.

Looking back at the centre of the Solar System – and directly at the Sun – poses some risk to the sensitive detectors in the probe’s long-range camera, however. So, no imaging effort will occur until New Horizon’s main mission objectives are achieved.

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

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MIT developed a simulation to determine the best way to deflect an asteroid – TechSpot



Why it matters: Barring self-inflicted catastrophes like nuclear war or irreversible climate change, the biggest threat to humanity is likely to come from outer space in the form of a rogue asteroid. It’s the type of fodder that makes for a decent blockbuster film but the truth is, it’s a very real concern.

Scientists for decades have theorized how to avoid an impact and now, researchers have gone so far as to lay out a framework to help determine what method of intervention would be best to mitigate a threat.

Their decision method accounts for multiple factors including an asteroid’s mass and momentum, the amount of time scientists would have before an impending collision and its proximity to a gravitational keyhole, among others.

Sung Wook Paek, lead author of a paper appearing in the journal Acta Astronautica this month, said people have mostly considered strategies of last-minute deflection, when an asteroid is heading toward a collision with Earth. “I’m interested in preventing keyhole passage well before Earth impact. It’s like a preemptive strike, with less mess,” the researcher said.

Paek and his team developed a simulation to help determine the best type of defense based on an asteroid’s various properties. The simulation was tested with Apophis and Bennu, asteroids in which researchers already know the locations of their gravitational keyholes, with a variety of variables.

Time seemed to be the major differentiator. For example, with Apophis, if they have at least five years before it will pass through a keyhole, there would be time to send two scouts out – one to measure the asteroid’s dimensions and another to nudge it slightly off track as a test before sending a main impactor to deflect it at a later date. If keyhole passage is set to occur between two and five years out, there may only be time for a single scout. Should the asteroid pass through a keyhole within a year or less, it could be too late to intervene.

Using the simulation tool, Paek and team may be able to set up alternative deflection methods in the future, such as launching projectiles from the Moon or using defunct satellites as kinetic impactors.

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The Earliest Sex Between Different Human Ancestors May Have Occurred 700,000 Years Ago – ScienceAlert



Our evolutionary history is full of inter-species sex.

Different human ancestor species seem to have mingled and mated far more than anthropologists previously realised. Neanderthals interbred with modern humans. Homo sapiens had sex with Denisovans.

And 700,000 years ago, according to a new study, a population of ancient humans mated with a distinct, unknown population that had separated from other human species at least 1 million years prior.

“This continues the story that we’ve been seeing in studies throughout the past decade: There’s lots more interbreeding between lots of human populations than we were aware of ever before,” Alan Rodgers, an anthropologist and the lead author of the new study, told Business Insider.

“This discovery has pushed the time depth of those interbreedings much farther back.”

According to his team’s research, published today in the journal Science Advances, the newly discovered interbreeding event took place in Eurasia, and it represents the earliest known example of mating between different populations of ancient humans.

The analysis, which compared DNA from Neanderthals, Denisovans, and modern humans from Europe and Africa, lends further credence to the idea that the our ancestors’ genes (and our own) came from myriad sources.

The oldest episode of interbreeding in the anthropological record

When geneticists finished sequencing the Neanderthal genome in 2010, they realised that Neanderthals had interbred with modern humans between 40,000 and 60,000 years ago.

Then a 2018 study revealed that Denisovans – which disappeared about 50,000 years ago – passed on some of their genes to Homo sapiens.

But the interbreeding event that Rodgers and his colleagues found was far, far older. In that case, a group of humans who were ancestors of both Neanderthals and Denisovans (the study authors nicknamed them “neandersovans”) interbred with their predecessor species about 744,000 years ago.

Those predecessors, in turn, were part of a”superarchaic” group in Eurasia that was between 20,000 and 50,000 people in size.

A major implication of the study, then, is that human populations migrated from Africa to Eurasia three times during our long evolutionary history: once 1.9 million years ago, again 700,000 years ago, and then a final time 50,000 years ago.

The first of these waves involved the “superarchaics”. Then the neandersovans followed 700,000 years ago; they likely separated from the modern human lineage before they migrated north, the study suggests.

As that second wave of ancestors moved into Eurasia, the researchers wrote, they likely “interbred with indigenous Eurasians, largely replaced them, and separated into eastern and western subpopulations – Denisovans and Neanderthals.”

Then many hundreds of thousands of years later, modern humans left Africa, interbreeding with Neanderthals – and eventually Denisovans, too – as they spread through Eurasia.

“These same events unfolded once again around 50,000 years ago as modern humans expanded out of Africa and into Eurasia, largely replacing the Neanderthals and Denisovans,” the study authors wrote.

A population of ‘superarchaic humans’

Rodgers’ team’s discovery came after they compared publicly available modern human DNA with ancient DNA. The analysis revealed at least four watershed moments in which genetic material passed from one human species to another over the last 1 million years.

Three of those moments matched the results other studies had already found. But the oldest instance was a new find.

In addition to representing the oldest evidence of human interbreeding on record, the finding is also surprising because but the two populations that mated were far less closely related than other human groups previously known to have interbred.

Whereas modern humans and Neanderthals had been on separate branches of the evolutionary tree for about 750,000 years when they interbred, the newly discovered population and the “neandersovans” had been separated for more than 1 million years.

Several mysteries remain, however. Rodgers’ team isn’t sure what ancient species the “superarchaic” population belonged to.

All they know is that genetic evidence suggests the superarchaics separated from our human lineage about 2 million years ago, and that ancient humans were living in Eurasia at the time the species separation occurred.

“We’ve got fossil evidence of humans in Eurasia that dates back to 1.85 million years old,” Rogers said.

At least two groups of human species, or taxa, lived in Eurasia during the time the superarchaics broke off from our lineage. One, Homo erectus, was the first of our ancestors to walk upright. The other possible taxon was Homo erectus’ younger cousin, Homo antecessor, which inhabited modern-day Spain.

“Any of those taxa might be the superarchaics,” Rodgers said. “Or they might be some taxon we don’t know about yet.”

But regardless of which group the superarchaics belonged to, Rodgers said, the new evidence of interbreeding offers a glimpse into an ancient time period that researchers know very little about.

“We’re just shedding light on an interval on human evolutionary history that was previously completely dark,” he said.

This article was originally published by Business Insider.

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University of Alberta scientist to participate in NASA Mars mission – CTV News



Chris Herd might not be going to the Red Planet himself but he’ll play a key role in NASA’s Mars 2020 rover project slated to launch this summer.

Herd, a professor in the Department of Earth and Atmospheric Sciences at the University of Alberta, has been chosen to analyze rock samples collected and stored with the intention of bringing them back to Earth through future missions to Mars.

“It was around the age of 13 that I wanted to work on rocks from Mars,” said Herd. “I wanted to be there when the rocks came back so for me to be chosen to be involved in a big mission and NASA’s next big mission to Mars, and the fact that it’s going to be collecting samples that will eventually come back to Earth, that really is the most exciting thing.”

The project marks the first time Martian meteorite and rock will be collected and stored. The hope is that the samples will provide key information about the planet’s geological history.

“We think that Mars may have had the conditions right for life at one point … especially the rocks that we’re going to look at,” said Herd. “So eventually the idea is to bring these samples back and really pour over them and tell us whether these actually have evidence for ancient life in them or not.”

Herd is one of 10 experts and the only Canadian selected by NASA for the project.

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