Tag: space

Scientists have found the best evidence yet for water just beneath the surface of Jupiter’s icy moon, Europa.

Analysis of the moon’s surface suggests plumes of warmer water well up beneath its icy shell, melting and fracturing the outer layers.

The results, published in the journal Nature, predict that small lakes exist only 3km below the crust.

Any liquid water could represent a potential habitat for life.

From models of magnetic forces, and images of its surface, scientists have long suspected that a giant ocean, roughly 160km (100 miles) deep, lies somewhere between 10-30km beneath the ice crust.

Many astrobiologists have dreamed of following in the footsteps of Arthur C Clarke’s fictional character David Bowman, who, in the novel Odyssey Two, discovers aquatic life-forms in the deep Europan sea.

But punching holes through the moon’s thick, icy outer layers has always seemed untenable.

The discovery of shallow liquid water by an American team makes a space mission to recover water from the moon much more plausible.

Shallow seas

The presence of shallow lakes also means that surface waters are probably vigorously mixing with deeper water.The icy eddies could transfer nutrients between the surface water and the ocean’s depths.

“That could make Europa and its ocean more habitable,” said lead author Britney Schmidt from the University of Texas at Austin, US, who analysed images collect by the Galileo spacecraft launched in 1989.

Glaciologists have been studying the surface of Europa for many years, trying to work out what formed its scarred, fractured surface.

By looking at Antarctica, where we see similar [features] – glaciers, ice shelves – we can infer something about the processes that are happening on Europa, said glaciologist Martin Siegert from the University of Edinburgh.

He explained that the new study tells us how upwelling of warmer water causes melting of surface ice, forming cracks.

“You get freezing [water] between the cracks… so you end up with the existing ice cemented in with new ice.”

“The underside then freezes again, which causes the uplifting; its pretty neat,” Dr Siegert told BBC News.

The US and Europe are working on missions to Europa, and Jupiter’s other moons, which they hope to launch either late this decade or early in the 2020s.

Europa

• Europa was discovered – together with three other satellites of Jupiter – by Italian astronomer Galileo Galilei in January 1610.
• The icy moon is 350 million miles from Earth, and is one of 64 Jovian satellites.
• In the 1990s, Nasa’s Galileo probe sent pictures back of its surface.
• Europa has a small metal core (light blue, centre), surrounded by a large layer of rock (orange).
• The surface is thought to consist of an ocean of liquid water (blue) covered by a thick layer of ice (beige).

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Scientists have discovered that Venus has an ozone layer.

The thin layer, hundreds of times less dense than the Earth’s, was discovered by the European Space Agency’s (Esa) Venus Express craft, researchers report in the journal Icarus.

Until now, ozone layers have only been detected in the atmospheres of Earth and Mars, and the discovery on Venus came as a surprise.

The find could help astronomers refine their hunt for life on other planets.

The European spacecraft spied the ozone layer when focusing on stars through Venus’ atmosphere.

The distant stars appeared fainter than expected, because the ozone layer absorbed some of their ultraviolet light.

The paper’s lead author Franck Montmessin, of the LATMOS atmospheric research centre in France, explained that Venus’ ozone layer sits 100km up; about three times the height of our own.

The ozone – a molecule containing three oxygen atoms – formed when sunlight broke down carbon dioxide in the Venusian atmosphere to form oxygen molecules.

On Earth, ozone, which absorbs much of the Sun’s harmful UV-rays preventing them reaching the surface, is formed in a similar way.

However, this process is supplemented by oxygen released by carbon dioxide-munching microbes.

Ozoning in

Speaking of the international team’s find, Hakan Svedhem, ESA project scientist for the Venus Express mission, said: “This ozone detection tells us a lot about the circulation and the chemistry of Venus’s atmosphere.

“Beyond that, it is yet more evidence of the fundamental similarity between the rocky planets, and shows the importance of studying Venus to understand them all.”

Some astrobiologists assume that the presence of oxygen, carbon, and ozone in an atmosphere indicates that life exists on a planet’s surface.

The new results negate that assumption – the mere presence of oxygen in an atmosphere is now not enough evidence to start looking for life.

However, the presence of large quantities of these gases, as in the Earth’s atmosphere, is probably still a good lead, the scientists said.

“We can use these new observations to test and refine the scenarios for the detection of life on other worlds,” said Dr Montmessin.

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Astronomers have spied a star’s swan song as it is shredded by a black hole.

Researchers suspect that the star wandered too close to the black hole and got sucked in by the huge gravitational forces.

The star’s final moments sent a flash of radiation hurtling towards Earth.

The energy burst is still visible by telescope more than two-and-a-half months later, the researchers report in the journal Science.

The Swift spacecraft constantly scans the skies for bursts of radiation, notifying astronomers when it locates a potential flare.

These bursts usually indicate the implosion of an ageing star, which produces a single, quick blast of energy.

But this event, first spotted on 28 March 2011 and designated Sw 1644+57, does not have the marks of an imploding sun.

What intrigued the researchers about this gamma ray burst is that it flared up four times over a period of four hours.

Astrophysicist Dr Andrew Levan from the University of Warwick, and his colleagues suspected that they were looking at a very different sort of galactic event; one where a passing star got sucked into a black hole.

The energy bursts matched nicely with what you might expect when you “throw a star into a black hole”, Dr Levan told BBC News.

Gasless centres

Black holes are thought to reside at the centres of most major galaxies. Some black holes are surrounded by matter in the form of gas; light is emitted when the gas is dragged into the hole. However, the centres of most galaxies are devoid of gas and so are invisible from Earth.

These black holes only become visible when an object such as a star is pulled in. If this happens, the star becomes elongated, first spreading out to form a “banana shape” before its inner edge – orbiting faster than the outer edge – pulls the star into a disc-shape that wraps itself around the hole.

As material drops into the black hole it becomes compressed and releases radiation that is usually visible from Earth for a month or so.

Events like these, termed mini-quasars, are incredibly rare – researchers expect one every hundred million years in any one galaxy.

The researchers used some of most powerful ground-based and space-based observatories – the Hubble Space Telescope, the Chandra X-ray Observatory and the Gemini and Keck Telescopes.

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Mars formed in record time, growing to its present size in a mere three million years, more quickly than scientists previously thought.

Its rapid formation could explain why the Red Planet is about one tenth the mass of Earth.

The study supports a 20-year-old theory that Mars remained small because it avoided collisions with planetary building material.

The new finding is published in the journal Nature.

In our early Solar System, well before planets had formed, a frisbee-shaped cloud of gas and dust encircled the Sun.

Scientists believe that the planets grew from material pulled together by electrostatic charges – the same force that’s behind the “dust bunnies” under your bed.

These proto-planetary dust balls grew and grew until they formed what scientists term “embryo” planets.

These rocky masses were large enough to exert a considerable gravitational force on surrounding material, including other nascent planets.

Nudging each other with their gravitational fields, the embryos were often thrown from their regular orbits, sometimes into the path of another large rocky mass.

If collisions occurred, these nascent planets were either expelled from the Solar System or shattered into pieces. These pieces were often combined to form a larger planet. In fact, the Earth’s Moon is thought to be the result of an embryo planet colliding with our own planet.

By modelling this process, astro-physicists can determine the size of planets they expect to form at a given distance from the Sun. Mars is an outlier; it should have grown to around the size of the Earth, but remains about one-tenth its size.

Because of Mars’ small size, many scientists have long suspected that the Red Planet avoided the collisions that allowed other neighbouring planets to increase their girth.

Red Runt

By studying the chemical composition of meteorites, geochemist Dr Nicholas Dauphas of the University of Chicago in Illinois and Dr Ali Pourmand of the University of Miami in Florida joined forces to try to confirm this.

By measuring the concentration of elements Thorium and Hafnium in 44 space-rocks Dr Pourmand and Dauphas have come up with the most precise estimate of the time it took Mars to form.

Between 2 and 3 million years they suspect; short compared to the Earth, which is thought to have taken tens of millions of years to grow to its current size.

“We were pleasantly surprised because now we have precise evidence in support of the idea… that Mars is a stranded planetary embryo”, Dr Pourmand told BBC News.

He thinks that Mars was around more or less in its current size when the Earth was beginning to form.

Given this, Mars could not have experienced the same type of growth as the Earth and Venus, says Dr Pourmand.

It’s likely that Mars remains small because it deftly avoided colliding with other planets.

“The fact that Mars appears to have been left unscathed could just be down to luck,” says astrophysicist Dr Duncan Forgan of the University of Edinburgh, UK.

He explains that while it is unlikely that a planet could escape collisions for such long periods, statistically one expects it to happen from time to time.

When modelling planetary dynamics, researchers find it easier to predict what happens in general, he says, but it is much more difficult to determine what happens in specific solar systems, or in specific cases like Mars.

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The precise spot at which a space storm struck the Earth’s outer atmosphere has been pinpointed for the first time.

These storms are caused by the bending and stretching of the Earth’s magnetic field by material from the Sun.

Observations like this may one day lead to better forecasting of these events, a meeting of the American Geophysical Union in Toronto, Canada, has heard.

This would provide more time to power down satellites and electrical grids, which can be damaged by these storms.

“If we can start to understand when and why these space storms occur, then we can try to move from short-term forecasting to long-term forecasting,” Dr Jonathan Rae, from the University of Alberta, told BBC News.

Space storms are the result of billions of tonnes of material thrown into space by the Sun in great plumes.

These plumes stretch the planet’s magnetic field like an elastic band, distorting the field from its usual circular shape to a long ellipse that reaches out behind our planet.

Eventually, when the field can stretch no further, it snaps back into place, rocketing particles into the Earth’s upper atmosphere. This causes the auroral displays known as the northern and southern lights.

It also floods the space in the planet’s immediate vicinity with radiation at such huge levels that they would endanger the lives of astronauts. This process also generates electrical surges on the ground capable of disrupting a country’s power grid.

Dr Rae led a team of scientists who took measurements of changes in the Earth’s magnetic fields using a system of cameras and magnetic instruments on the ground, while simultaneously observing the onset of a space storm from Nasa’s five-strong fleet of THEMIS spacecraft.

They saw magnetic oscillations hit the upper atmosphere in a particular location – somewhere over Canada – and ripple out across the ionosphere. These events were followed, three minutes later, by an auroral display.

Researchers hope to use these observations to better predict these events. This could lead to the forecasting of storms hours, or even days, before they occur.

This would give more advanced warnings, helping protect humans and equipment from the radiation generated by disturbances.

“In the future, we should be able to predict space weather in the same way that we now can predict long-term weather forecasts [on Earth],” Dr Rae said.

Space storms are expected to increase as the Sun approaches another solar maximum. This is predicted to occur again by 2013 – when the influence of the Sun on the Earth’s magnetic field will be greatest.

The work is reported in the Journal of Geophysical Research and is co-funded by the Canadian Space Agency and Nasa.

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