Did Earth receive its water from comets, or geologically from within?

A new study is helping to answer a long-standing question that has recently moved to the forefront of 

earth science: did our planet make its own water through geologic processes, or did water come to us via icy comets^[1] from the far reaches of the Solar System?

The answer is likely “both,” according to researchers at The Ohio State University — and the same amount of water that currently fills the Pacific Ocean could be buried deep inside the planet right now.

At the American Geophysical Union (AGU) meeting on Wednesday, 17th December, they reported the discovery of a previously unknown geochemical pathway by which the Earth can sequester water in its interior for billions of years and still release small amounts to the surface via plate tectonics, feeding our oceans from within.

In trying to understand the formation of the early Earth, some researchers have suggested that the planet was dry and inhospitable to life until icy comets pelted the earth and deposited water on the surface.

Wendy Panero, associate professor of earth sciences at Ohio State, and doctoral student Jeff Pigott are pursuing a different hypothesis: that Earth was formed with entire oceans of water in its interior, and has been continuously supplying water to the surface via plate tectonics ever since.

Researchers have long accepted that the mantle contains some water, but how much water is a mystery. And, if some geological mechanism has been supplying water to the surface all this time, wouldn’t the mantle have run out of water by now?

Because there’s no way to directly study deep mantle rocks, Panero and Pigott are probing the question with high-pressure physics experiments and computer calculations.

“When we look into the origins of water on Earth, what we’re really asking is, why are we so different than all the other planets?” Panero said. “In this solar system, Earth is unique because we have liquid water on the surface. We’re also the only planet with active plate tectonics. Maybe this water in the mantle is key to plate tectonics, and that’s part of what makes Earth habitable.”

Central to the study is the idea that rocks that appear dry to the human eye can actually contain water — in the form of hydrogen atoms trapped inside natural voids and crystal defects. Oxygen is plentiful in minerals, so when a mineral contains some hydrogen, certain chemical reactions can free the hydrogen to bond with the oxygen and make water.

Stray atoms of hydrogen could make up only a tiny fraction of mantle rock, the researchers explained. Given that the mantle is more than 80 percent of the planet’s total volume, however, those stray atoms add up to a lot of potential water.

In a lab at Ohio State, the researchers compress different minerals that are common to the mantle and subject them to high pressures and temperatures using a diamond anvil cell — a device that squeezes a tiny sample of material between two diamonds and heats it with a laser — to simulate conditions in the deep Earth. They examine how the minerals’ crystal structures change as they are compressed, and use that information to gauge the minerals’ relative capacities for storing hydrogen. Then, they extend their experimental results using computer calculations to uncover the geochemical processes that would enable these minerals to rise through the mantle to the surface — a necessary condition for water to escape into the oceans.

In a paper now submitted to a peer-reviewed academic journal, they reported their recent tests of the mineral bridgmanite, a high-pressure form of olivine. While bridgmanite is the most abundant mineral in the lower mantle, they found that it contains too little hydrogen to play an important role in Earth’s water supply.

Another research group recently found that ringwoodite, another form of olivine, does contain enough hydrogen to make it a good candidate for deep-earth water storage. So Panero and Pigott focused their study on the depth where ringwoodite is found — a place 325-500 miles below the surface that researchers call the “transition zone” — as the most likely region that can hold a planet’s worth of water. From there, the same convection of mantle rock that produces plate tectonics could carry the water to the surface.

One problem: If all the water in ringwoodite is continually drained to the surface via plate tectonics, how could the planet hold any in reserve?

For the research presented at AGU, Panero and Pigott performed new computer calculations of the geochemistry in the lowest portion of the mantle, some 500 miles deep and more. There, another mineral, garnet, emerged as a likely water-carrier — a go-between that could deliver some of the water from ringwoodite down into the otherwise dry lower mantle.

If this scenario is accurate, the Earth may today hold half as much water in its depths as is currently flowing in oceans on the surface, Panero said—an amount that would approximately equal the volume of the Pacific Ocean. This water is continuously cycled through the transition zone as a result of plate tectonics.

“One way to look at this research is that we’re putting constraints on the amount of water that could be down there,” Pigott added.

Panero called the complex relationship between plate tectonics and surface water “one of the great mysteries in the geosciences.” But this new study supports researchers’ growing suspicion that mantle convection somehow regulates the amount of water in the oceans. It also vastly expands the timeline for Earth’s water cycle.

“If all of the Earth’s water is on the surface, that gives us one interpretation of the water cycle, where we can think of water cycling from oceans into the atmosphere and into the groundwater over millions of years,” she said. “But if mantle circulation is also part of the water cycle, the total cycle time for our planet’s water has to be billions of years.”

http://astronomynow.com/2014/12/21/did-earth-receive-its-water-from-comets-or-geologically-from-within/

Astronomy: Any evidence of life on Mars likely in deep rock

Although I’ve written about this in previous years, the new data from Curiosity now show much stronger evidence than before that Mars once had large lakes or perhaps even an ocean.

Layer upon layer of sedimentary rock clearly shows that Mars had more than just a bit of water on its surface in the past. In fact, it once had a large body of water that lasted many millions of years.

That is long enough to imagine that life (in the form of microorganisms) might have taken hold on Mars before going extinct.

There still is no direct evidence of microbial life ever being present on Mars, but the environment there billions of years ago appears to have been suitable for sustaining life. Before Curiosity, this idea was speculative. Now, the evidence is nearly undeniable.

Even though Curiosity still has a lot of work to do, we can start thinking about the next step: a dedicated mission to look for possible fossil evidence of long-ago microbial life on Mars. Although Curiosity can detect organic material, its primary mission was to look for geological evidence of a habitat that could sustain life. This it has done well. But finding evidence of primordial life is another matter.

If you think about fossils on Earth, usually what comes to mind is the imprint of bones left in a rock after a dead animal decomposed and then was covered by sediment. Over many years — and more layers of sediment — the dirt becomes rock and the bones leave a telltale impression.

The problem on Mars is, of course, that microbial life has no bones. The only evidence that would remain is organic molecules that are typically made by living things. Over long periods of time, even these organic compounds would undergo chemical reactions, leaving little trace of their existence.

Searching for evidence of organics is further complicated because simple organic molecules are found in meteorites, which constantly bombard Mars (and other planets). What we really need to find are complex organic molecules, and if these exist, they probably are locked deep underground, where Curiosity can’t go.

Curiosity has drilled an inch or so into rocks and found organic compounds. Although this is promising, there still is no “smoking gun” discovery of organics unique to Mars.

This all leads to the suggestion that a manned mission to Mars is necessary. Advocates of this mission say that only humans have the flexibility to fully investigate Martian rocks for evidence of life.

I might agree with this in principle, but I think it’s much better to bring rocks back to Earth rather than transport humans to Mars. Sending humans to Mars would contaminate the landscape. If you’re trying to find a tiny grain of sand on a pristine floor, you don’t walk all over the floor with dirty shoes.

A human mission would spread organic materials into the Martian environment, while robots such as Curiosity are relatively clean. Of course, even robots need to get to Mars, and this would be easier with the new rockets being built by NASA.

The Space Launch System, which would be more powerful than the older Delta IV rocket, will be tested in 2017. This new rocket makes possible a mission to bring Mars rocks back to Earth for better analysis.

http://full-timewhistle.com/science-27/astronomy-any-evidence-of-life-on-mars-likely-in-deep-rock-524.html

Signs of Europa plumes remain elusive in search of Cassini data

The new research shows that the jovian moon’s atmosphere is actually about 100 times less dense than previously thought.

A fresh look at data collected by NASA’s Cassini spacecraft during its 2001 flyby of Jupiter shows that Europa’s tenuous atmosphere is even thinner than previously thought and also suggests that the thin hot gas around the moon does not show evidence of plume activity occurring at the time of the flyby. The new research provides a snapshot of Europa’s state of activity at that time and suggests that if there is plume activity it is likely intermittent.

Europa is considered one of the most exciting destinations in the solar system for future exploration because it shows strong indications of having an ocean beneath its icy crust.

Members of Cassini’s ultraviolet imaging spectrograph (UVIS) team analyzed data collected by their instrument during the brief time it observed Europa in 2001 as Cassini sped through the Jupiter system en route to Saturn. The observations show that most of the hot excited gas, or plasma, around Europa originates not from the moon itself, but from volcanoes on the nearby moon Io. In fact, from their data, the researchers calculated that Europa contributes 40 times less oxygen than previously thought to its surrounding environment.

“Our work shows that researchers have been overestimating the density of Europa’s atmosphere by quite a bit,” said Don Shemansky from Space Environment Technologies in Pasadena, California. The team found that the moon’s tenuous atmosphere, which was already thought to be millions of times thinner than Earth’s atmosphere, is actually about 100 times less dense than those previous estimates.

A downward revision in the amount of oxygen Europa pumps into the environment around Jupiter would make it less likely that the moon is regularly venting plumes of water vapor high into orbit, especially at the time the data was acquired.

Scientists would expect that ongoing plume activity at Europa, as Cassini has observed at Saturn’s moon Enceladus, would inject large amounts of water vapor into the area around Europa’s orbit if the plumes were large enough, but that is not what UVIS observed.

“We found no evidence for water near Europa, even though we have readily detected it as it erupts in the plumes of Enceladus,” said Larry Esposito from the University of Colorado, Boulder.

“It is certainly still possible that plume activity occurs, but that it is infrequent or the plumes are smaller than we see at Enceladus,” said Amanda Hendrix from the Planetary Science Institute in Pasadena. “If eruptive activity was occurring at the time of Cassini’s flyby, it was at a level too low to be detectable by UVIS.”

Indications of possible plume activity were reported in 2013 by researchers using NASA’s Hubble Space Telescope, launching a wave of interest in searching for additional signs, including this effort by the UVIS team. Cassini’s 2001 Jupiter flyby provided UVIS the opportunity to directly measure the environment near Europa, which is not possible with Hubble.

For more than a decade, Cassini’s UVIS has observed the cold dense doughnut of gas that encloses the orbit of Enceladus. There, the massive amount of gas being breathed into orbit around Saturn by the Enceladus plumes acts like a brake on electrons being dragged through it by Saturn’s magnetic field, which rotates with the planet. This braking helps to keep down the temperature of the plasma. Apparently there is no such brake at Europa.

Since UVIS saw a hot plasma rather than a cold one around Europa’s orbit, it suggests Europa is not outputting large amounts of gas, including water.

Snapshots provided by missions that visited Jupiter prior to Cassini provided strong indications that Io is the major contributor of material to the environment around Jupiter, and indicated a hot low density plasma surrounding Europa. The new results confirm that. “Io is the real monster here,” Shemansky said.

“Europa is a complex, amazing world, and understanding it is challenging given the limited observations we have,” said Curt Niebur from NASA Headquarters in Washington, D.C. “Studies like this make the most of the data we have and help guide the kinds of science investigations NASA should pursue in the future.”

Scientists are currently using the Hubble Space Telescope to conduct an extensive six-month-long survey looking for plume activity, and NASA is also studying various possible Europa missions for future exploration.

http://www.astronomy.com/news/2014/12/signs-of-europa-plumes-remain-elusive-in-search-of-cassini-data

Europe’s Venus Express mission is at its end

The European Space Agency’s Venus Express spacecraft has run out of fuel and will burn up in the atmosphere of Venus in January after a successful eight-year mission.

Ground controllers lost contact with Venus Express on Nov. 28 after a planned maneuver to raise the altitude of the craft’s orbit around Venus in hopes of keeping the mission going into 2015.

Håkan Svedhem, ESA’s Venus Express project scientist, said mission control has received intermittent telemetry from the spacecraft since late November. The data signature indicates the orbiter is in a spin and can only contact Earth when its antennas happen to be pointing the right direction.

Complicating matters, Venus is near the farthest point from Earth as the planets orbit around the sun, so radio signals from Venus Express are very week, Svedhem said.

Venus Express was programmed to execute a series of rocket burns to boost its orbit from Nov. 23 to Nov. 30 to keep the spacecraft from entering the Venusian atmosphere.

“The available information provides evidence of the spacecraft losing attitude control most likely due to thrust problems during the raising maneuvers,” said Patrick Martin, ESA’s Venus Express mission manager. “It seems likely, therefore, that Venus Express exhausted its remaining propellant about half way through the planned maneuvers last month.”

Officials knew the fuel and oxidizer tanks aboard Venus Express were running low, but spacecraft do not carry a fuel gauge, so engineers were not sure how much propellant was left on the orbiter.

“It is difficult to quantify the probability, but I would say that it is very likely that the fuel in the tanks is at least so much depleted that we sometimes get gas bubbles in the fuel lines,” Svedhem said in an email to Spaceflight Now. “There might still be some limited amount of fuel in the tanks but this is not accessible.”

Without propellant to maintain its altitude, Venus Express will succumb to atmospheric drag and fall out of orbit some time around mid-January, Svedhem said.

The probe will be crushed by the pressure of the Venusian atmosphere, disintegrating in a ball of plasma dozens of miles above the planet.

The spacecraft arrived at Venus in April 2006 after five-month cruise from Earth, entering an egg-shaped orbit for a planned 500-day mission.

ESA granted extra funding to continue the mission, including a final tranche of money approved in November to extend Venus Express operations into 2015 until it exhausted its fuel supply.

“After over eight years in orbit around Venus, we knew that our spacecraft was running on fumes,” said Adam Williams, ESA’s acting Venus Express spacecraft operations manager. “It was to be expected that the remaining propellant would be exhausted during this period, but we are pleased to have been pushing the boundaries right down to the last drop.”

Controllers used the last bit of fuel inside the spacecraft to move its orbit closer to Venus in from May to July, exploring deeper inside the Venusian atmosphere and gathering data on aerobreaking, a technique that future missions could use to shape their orbits around planets like Venus.

Venus Express spent most of its mission circling the planet in an orbit with a point closest to Venus about 120 miles (200 kilometers) above its surface. The orbit typically took the spacecraft 41,000 miles (66,000 kilometers) from Venus at its highest altitude.

The aerobreaking campaign this year involved flying Venus Express as low as 80 miles (130 kilometers) above the planet. When the experiments were finished, engineers raised the low point of the craft’s orbit to an altitude of about 285 miles (460 kilometers).

But the orbit naturally decayed and Venus Express fell closer to the upper reaches of the atmosphere, causing officials to decide to boost its orbit again in a bid to extend its mission by a few months.

It turns out there was not enough propellant left in the probe’s tanks to complete the orbit-raising maneuvers.

Venus Express was built out of spare parts from ESA’s Mars Express and Rosetta missions and launched in November 2005. ESA developed and launched the low-budget mission for 220 million euros, or about $270 million, at 2005 values.

Scientists say the mission found evidence of lava flows on Venus indicating active volcanism within the last 2.5 million years. It also sensed fluctuations in concentrations of sulphur dioxide in the upper atmosphere, a finding that could be explained by volcanic activity.

The orbiter’s instruments measured wind speeds rose in the smothering Venusian atmosphere over a six-year period.

The spacecraft discovered that a day on Venus — which lasts 243 Earth days — had shortened by six-and-a-half minutes since NASA’s Magellan mission measured the planet’s rotation more than 20 years ago.

Data from Venus Express also support the theory that the planet was once more hospitable for life, with measurements indicating Venus once harbored significant water, perhaps enough to fill oceans on its surface, according to an ESA press release.

“During its mission at Venus, the spacecraft provided a comprehensive study of the planet’s ionosphere and atmosphere, and has enabled us to draw important conclusions about its surface,” Svedhem said in an ESA press release. “While the science collection phase of the mission is now complete, the data will keep the scientific community busy for many years to come.”

With the end of the Venus Express mission, no more spacecraft are operating at Earth’s sister planet.

Japan’s Akatsuki mission is due to arrive at Venus in November 2015 after missing a chance to enter orbit there in late 2010. Japanese officials blamed the 2010 failure on a glitch in the probe’s main engine, and engineers plan to use smaller thrusters to help Venus capture the spacecraft in orbit.

http://astronomynow.com/2014/12/19/europes-venus-express-mission-is-at-its-end/

“Tsunami wave” still flies through interstellar 

space

This shock wave that Voyager I is experiencing is the longest lasting wave that 

researchers have seen.

The “tsunami wave” that NASA’s Voyager 1 spacecraft began experiencing earlier this year is still propagating outward, according to new results. It is the longest-lasting shock wave that researchers have seen in interstellar space.

“Most people would have thought the interstellar medium would have been smooth and quiet. But these shock waves seem to be more common than we thought,” said Don Gurnett from the University of Iowa in Iowa City.

A “tsunami wave” occurs when the Sun emits a coronal mass ejection, throwing out a magnetic cloud of plasma from its surface. This generates a wave of pressure. When the wave runs into the interstellar plasma — the charged particles found in the space between the stars — a shock wave results that perturbs the plasma.

“The tsunami causes the ionized gas that is out there to resonate — ‘sing’ or vibrate like a bell,” said Ed Stone from the California Institute of Technology in Pasadena.

This is the third shock wave that Voyager 1 has experienced. The first event was in October to November 2012, and the second wave in April to May 2013 revealed an even higher plasma density. Voyager 1 detected the most recent event in February, and it is still going on as of November data. The spacecraft has moved outward 250 million miles (400 million kilometers) during the third event.

“This remarkable event raises questions that will stimulate new studies of the nature of shocks in the interstellar medium,” said Leonard Burlaga from the NASA Goddard Space Flight Center in Greenbelt, Maryland, who analyzed the magnetic field data that were key to these results.

It is unclear to researchers what the unusual longevity of this particular wave may mean. They are also uncertain as to how fast the wave is moving or how broad a region it covers.

The second tsunami wave helped researchers determine in 2013 that Voyager 1 had left the heliosphere, the bubble created by the solar wind encompassing the Sun and the planets in our solar system. Denser plasma “rings” at a higher frequency and the medium that Voyager flew through was 40 times denser than what had been previously measured. This was key to the conclusion that Voyager had entered a frontier where no spacecraft had gone before: interstellar space.

“The density of the plasma is higher the farther Voyager goes,” Stone said. “Is that because the interstellar medium is denser as Voyager moves away from the heliosphere, or is it from the shock wave itself? We don’t know yet.”

Gurnett expects that such shock waves propagate far out into space, perhaps even to twice the distance between the Sun and where the spacecraft is right now.

Voyager 1 and its twin, Voyager 2, were launched 16 days apart in 1977. Both spacecraft flew by Jupiter and Saturn. Voyager 2 also flew by Uranus and Neptune. Voyager 2, launched before Voyager 1, is the longest continuously operated spacecraft and is expected to enter interstellar space in a few years.

http://www.astronomy.com/news/2014/12/tsunami-wave-still-flies-through-interstellar-space

Carnegie hosts Mercury crater-naming contest

The MESSENGER Education and Public Outreach (EPO) Team is launching a competition this week to name five impact craters on Mercury. The contest is open to all Earthlings, except for members of the mission’s EPO team. The contest runs from 15th December 2014 to 15th January 2015.

NASA’s MESSENGER spacecraft has been in orbit about Mercury since March 2011. The mission’s EPO team is led by Julie Edmonds of the Carnegie Institution for Science.

According to the International Astronomical Union (IAU) — the governing body of planetary and satellite nomenclature since 1919 — all new craters on Mercury must be named after an artist, composer, or writer who was famous for more than 50 years and has been dead for more than three years. See the current list of named Mercury craters.

http://astronomynow.com/2014/12/16/carnegie-hosts-mercury-crater-naming-contest/

http://adnanalshawafi.blogspot.com/

Some of us fear the impact of cuts in 2016 more than the research funding results

well, here we are. The work of 52,077 academic staff submitted, 191,232 of their “outputs” assessed, 10,099 early career researchers included, 6,975 “impact case studies” reviewed. That is a lot of staff, a lot of aspiring researchers and a lot of stories. What are we to make of it all? TheResearch Excellence Framework 2014 results are about to hit the headlines. Buckle up.

Across the UK, academics will be nervously logging on to the REF website on Thursday to see what their peers have made of their research from 2008 to 2013. Innovation, revelation, inspiration and, yes, consternation, reduced to a grading on a four-star scale. What is this thing, and what do we do with it?

It is not just the quality of research that has been assessed (65% weighting towards the overall score), it is also the “vitality” of the departmental research environment (15%) and, controversially, an assessment of “impact” (20%), in other words whether the research made any difference in the wider world.

Some of it was surreal. We were required to identify research-inactive staff and assign them to a unit of assessment. This raises epistemological problems: what is it precisely that Dr Smith has not been researching in? Is he not researching in astrophysics or not researching in computing? I once came across someone who claimed to be not researching in genetics and simultaneously not researching in neurobiology, on the reasoning that interdisciplinary approaches are so important these days. Such is the REF bureaucracy.

Of course, we should not underestimate the capacity of the results to stimulate research endeavour in its own right. I was impressed by the advances in set theory achieved by some university PR departments in 2008 when they created new branches of mathematics by promoting groupings that contained only the top 10 elements thereof. But we should also watch out for the “Woodstock effect” in which 90% of the researchers in a department will claim credit for the 5% of work classified in the four-star “world-leading” category. They can’t all have been in there.

As is well known, the “impact” component contractually compelled all researchers to sell their souls to the devil and invent cures for baldness overnight, or risk having their research classified as worthless.

I’ve never been convinced by the rating scale “world leading”, “internationally excellent”, “recognised internationally” and “recognised nationally”. Those aren’t four points on an ill-defined scale: they’re four ill-defined points on four different scales. It’s like rating chocolate on a scale of 1 to 4, where 1 is poor value for money, 2 melts well in the mouth, 3 is nicely presented and 4 is deliciously sweet

Allegations of selective submission have been rife. A two-star rating won’t attract funding, and this has led to the submission of only those with three-star work or better. However, keep a lookout for results which show that some well-funded universities have outputs rated as one-star or even “unclassified”. It is conceivable that some researchers have one potential Nobel prize-winning paper and just three other papers, one of which is one step above using crayons to colour in DNA sequences.

We need to have a real assessment of the return on investment in the REF. Some institutions produce extraordinary research results on levels of funding that are lower than individual faculties in other universities. Don’t get me wrong, we need to invest in our leading research departments, but we must fund excellence wherever it is found.

Yet money is eye-wateringly tight. When the autumn statement anticipates 40% post-election public spending cuts across the board, can the ringfence around the £4.6bn science research budget survive? Let’s hope it’s merely decimated. Initial allocations will be announced in April 2015, but 2016 will be when the real longer-term funding plans will be known.

Carping about league tables, value for money, impact and ratings is all good fun. But in the end, we should spend less energy aggregating ratings to determine marginal differences and instead celebrate that the UK is home to one of the world’s most vibrant research cultures. Undervalued, over-regulated, imperfect and spectacular in equal measure – but we should be proud of what we achieve. Heavy cuts would damage all this, and no amount of PR spin could fix that.

http://www.theguardian.com/education/2014/dec/16/fear-impact-cuts-research-funding