Sea Above, Sky Below

Sea above, sky below.  The phrase is seemingly a contradiction and a mental paradox.  Yet recent research into cosmology, astronomy and oceanography suggests that this riddle is perhaps not as irreconcilable as what it may first appear. Recalling Milton's evocation of the empty heavens as a kind of ocean, the inversion of sea and sky is taking place all around us, in physics and in oceanography.

The most important advances in scientific thought about the origins and structure of the universe now suggest that our world may be just one amongst many, floating in a cosmological sea. The space probe Cassini has revealed that even in the heavens above, oceans may in fact, be commonplace.  Radio astronomers describe the noise storms of Jupiter and its moon Io as sounding like ocean waves breaking up on the beach. And here on the firmament we are increasingly turning to the oceans in order to better understand the skies.

ALMA (the Atacama Large Millimetre/submillimetre Array)

After recently watching the documentary, Seeing Stars, which analyses the new generation of telescopes that enable scientists and engineers to do 'extreme astronomy', I was prompted to revisit some of the unusual techniques which are currently being used to probe the edges of our universe, which I first starting looking into a few years ago.
The documentary, by the way, is well worth watching:

The infant branch of astronomy, known as "neutrino astronomy" is motivated by the possibility of observing phenomena, such as cosmic neutrinos, that are inaccessible to optical telescopes.  Cosmic neutrinos, which are believed to be produced by cosmic rays, are very difficult to detect. By building arrays deep under water, astronomers can make sure that most of the particles they detect are actually produced by cosmic sources. These detectors look down through the Earth to see the universe, using the whole planet as a shield to absorb the riffraff of particles from the atmosphere.

One of the leading voices within oceanic neutrino science is Dr Paschal Coyle (pictured), who is based in Marseille in France.  His 2007 Journal of Physics paper, Neutrinos Out of the (Deep) Blue remains a valuable reference in surveying the various approaches to underwater neutrino observation.

He is a key researcher with the ANTARES observatory, which is situated under the Mediterranean Sea, 42km off the coast of Toulon. His team set out to monitor their below-sea telescope in the brilliantly named research vessel, Pourquoi Pas?.

ANTARES research vessel, Pourquois Pas?

ANTARES stands for "Astronomy with a Neutrino Telescope and Abyss environmental RESeach project", a rather clunkily assembled acronym, but one that figuratively at least, situates one of our most charismatic stars - Antares - deep under the sea.

The ANTARES detector comprises a total of 900 optical modules distributed over 12 flexible lines, each comprising 25 storeys.  They are anchored at the bottom of the sea at a depth of about 2.5 km, approximately 70 meters apart from each other.

Design visualisation of the ANTARES underwater detector modules

ANTARES is designed to detect neutrinos from space, coming from the direction of the Southern Hemisphere of Earth.  As neutrinos have no mass and no charge, they fly through matter as if it wasn't there, and are therefore fiendishly difficult to detect.  If a cosmic neutrino collided with Earth in the Southern Hemisphere, say for example in Australia, it would fly through the Earth and exit through the Mediterranean sea off southern France on it's way back out to space. ANTARES is constructed with the specific intention of detecting those elusive neutrinos on their ghostly and perpetual journey.  Occasionally, on its journey, a muon neutrino will interact with the water in the Mediterranean. When this happens, it will produce a high energy muon.

 

ANTARES works by detecting Cherenkov radiation (pictured) emitted as the muon passes through the water.  So ANTARES is a highly sensitive optical instrument designed to detect the uncanny blue glow of Cherenkov radiation caused by one of the rarest phenomena in existence.

Over the past four years, Paschal Coyle and his team, have made many expeditions to the underwater detector hunting for neutrinos.  Whilst they have detected many neutrinos - consistent with what might be found in the Earth's atmosphere at any one time - they haven't found a single cosmic neutrino.

To put it more formally, as the team did in their May 2012 abstract, "no significant neutrino signal in excess of that expected from atmospheric background has been found".  The team submitted a further paper to the Astrophysical Journal in July, and in it they emphasised, "no statistically significant signal has been found and upper limits on the neutrino flux have been obtained."

Despite this, the search goes on, and ANTARES has more than one function. As well as looking for particles of cosmic origin, and thus being an important part of the astrophysics community, ANTARES is also at the forefront of particle physics research, taking part in the search for dark matter. It complements the dark matter searches performed by experiments such as Fermilab's CDMS, and at CERN's dark matter work at the LHC.

ANTARES instrument panel aboard Pourquois Pas?

ANTARES' contribution to the field is to attempt to detect a hypothetical phenomena known as "neutralino annihilation", which is thought to take place in the Sun, or the centre of our galaxy.  The theoretical particle, the neutralino, is considered a good candidate for the substance of the universe's cold dark matter. To confirm its existence, neutrino telescopes, such as ANTARES, look for evidence of the annihilation of neutralinos in regions of high dark matter density such as the centres of stars or galaxies.  If ANTARES was able to detect this speculative phenomena, it would be a major breakthrough in our understanding of the universe.

A new generation of telescopes are analysing our skies in ever more novel ways: from vast radio arrays in arid desert mountains, to telescopes strapped to aircraft soaring into the stratosphere, to futuristic Air Fluorescence telescopes looking for high-energy cosmic rays. At the forefront of these techniques are telescopes built underwater, searching our skies from the depths of our oceans.

As it looks through the earth to detect neutrinos from space, ANTARES is peering at the sky below, from the sea above.

Dedication:

Sea Above, Sky Below is the title of a song by Dirty Three, which appears on the 1995 album, Ocean Songs. This post is dedicated to Peter Kirk.



Sources:
http://antares.in2p3.fr/Overview/index.html
http://www.iop.org/
http://arxiv.org/abs/1207.3105

Sail to The Moon

In one of the more poetic and outlandish stories this week, The Observer report that engineers are planning to build the first extraterrestrial boat.

They want to launch the craft towards Titan - Saturn's largest moon - and parachute it on to the Ligeia Mare, a sea of methane and ethane on its surface.

Robin McKie, Science Editor of The Observer writes, "the robot ship would sail around this extraterrestrial sea for several months, exploring its coastline and measuring the winds and waves that sweep its surface."

Professor John Zarnecki, of the Open University is one of the scientists working on the project. "Waves on Titan's seas will be far larger, but much slower, than on earthly oceans, according to our calculations. That suggests Titan is the best spot in the solar system for surfing."

The mission to Titan - the only moon in the solar system with a thick atmosphere, of nitrogen and methane - would be the first exploration of a sea beyond Earth and could provide evidence about the possible existence of complex organic chemicals, the precursors of life.

It is part of the proposed Titan Mare Explorer, or TiME project.

If TiME is selected from a shortlist of three possible missions being considered for funding by NASA, McKie explains that "the TiME probe will be fired at Titan on a billion-mile journey across the solar system. Once it enters the moon's thick atmosphere the craft would parachute down towards the surface and then drop into the 300-mile-wide Ligeia Mare. It would then spend several months afloat on an oily sea taking measurements of waves, chemicals and other variables."

It follows on from the research undertaken by Cassini-Huygens. In 2005, the space-probe, Cassini deployed Huygens on the surface of Titan. Many of the instruments for that craft were built by Zarnecki and his Open University team, and that experience will put them in good stead for the TiME mission, should it go ahead.

Full story: http://www.guardian.co.uk

Source: Titan.pdf

&: SailtoThe Moon

Listen to the Deep Ocean - live!

Last year, we reported on research published in Nature that showed how marine biologists were working hand-in-hand with physicists to use bio-acoustics technology for the dual purpose of monitoring marine live, and searching for neutrinos.

The recently launched Listening to the Deep Ocean Environment (LIDO) website takes this collaborative approach one step further. Michel André, a bioacoustician at the Technical University of Catalonia in Barcelona, Spain, and his colleagues, have spent the past 10 years placing hydrophones on the seabed, on existing research platforms that monitor earthquakes, tsunamis and detect neutrino particles from space.

They are studying sub-sea noise so that researchers can better understand the effects of human activity on whales and dolphins. But what's really extraordinary about their work is that they're allowing us to tune in. The LIDO website has links to live audio feeds from eleven hydrophones located in European waters, and North American waters.

André, quoted in the New Scientist, notes: "the system is powered from the shore, and streams audio data to a server where the signals are analysed and published directly on the internet."

With more hydrophones in the network the new system could reveal the effects of noise pollution on whales. Hydrophones can pick up sounds from baleen whales hundreds of kilometres away, so installations in different places could be used to triangulate an animal's position and track its course. It should therefore be possible to determine if animals change course in response to bursts of noise, or alter their preferred routes because of new sources of noise like shipping routes or harbours.

"It's the first time we have been able to monitor acoustic events on a large temporal and spatial scale," André says

An algorithm developed by André's laboratory filters the different frequencies in the signal to identify specific sounds, including the songs of 26 species of whales and dolphins, and noise from human activities such as shipping, wind farms, oil and gas drilling, and seismic testing.

Roger Gentry, an adviser for the E&P Sound and Marine Life Joint Industry Programme, comments that, "[Michel] André deserves a lot of credit for thinking in broad terms and using modern technology to make the oceans and marine mammals more familiar and accessible to us all."

André is a previous Rolex award-winner, acknowledged for his work designing a system to protect whales from collisions with ships: http://rolexawards.com/en/the-laureates/michelandre-biography.jsp

Sources: 

http://listentothedeep.net
http://www.newscientist.com

A drop in the ocean - the Census of Marine Life reveals we've only just begun

This week in London, the Census of Marine Life reported on their ten-year quest to count and document life in the world's oceans.

The discoveries made over the past decade have inspired, surprised and delighted all of us who have been following the work of this epic project, which has dramatically expanded our understanding of the underwater realm. But the Census team ended their work on a humble note, stressing that despite ten years of work, and the coordinated global effort of over 2,700 scientists from more than 600 institutions, who examined every oceanic body on the planet, during 9,000 days at sea on more than 540 expeditions, they have barely scratched the surface of the diversity and strangeness of life in the sea.

"There's a lot of ocean left to explore", says environmental scientist and Census cofounder, Jesse Ausubel.

Dr. Ian Poiner, chair of the Census Steering Committee, underscored the importance of this vast body of research by noting:

"All surface life depends on life inside and beneath the oceans. Sea life provides half of our oxygen and a lot of our food and regulates climate. We are all citizens of the sea. And while much remains unknown, including at least 750,000 undiscovered species and their roles, we are better acquainted now with our fellow travelers and their vast habitat on this globe."

Science News gets to grips with the scale of the work still to do, by observing that according to the Census summary, the tally of 16,764 marine fish species formally named as of early 2010 probably falls short by an estimated 5,000 species. And fish aren't the half of it. They're perhaps 12 percent of the total of marine species, according to the census estimates. Fishes trail after crustaceans and mollusks in number of species, and researchers report evidence of major undercounts in the numbers of recorded species for these other groups too. Overall at least 750,000 marine species, not including microbes, still await discovery, the census teams predict. In the seas, the mysteries easily outnumber known species, now estimated at 250,000.

Deep waters below 200 meters are so under-explored that their life forms constitute "biodiversity's big wet secret," says the census's chief scientist, Ron O'Dor of Dalhousie University in Halifax, Canada. Fewer than 10 percent of records of marine life come from the zone of abyssal plains between 4,000 and 5,000 meters deep, yet that zone accounts for half the oceans' area.

Sources: http://www.sciencedaily.com/releases/2010/10/101004101319.htm
http://www.sciencenews.org/view/generic/id/64013/description/Massive_count_a_...

The neutrino and the whale

A physicist recording underwater sounds has made an unexpected discovery.

An underwater effort to detect subatomic particles has ended up detecting sperm whales instead.

Nature reports on a reports on a partnership between marine biologists and particle physicists in Catania, in Eastern Sicily.

Source: http://www.nature.com/news/2009/091202/full/462560a.html

Rethinking Light and Sound

The director of the Census for Marine Life - Jesse Ausubel - rethinks how illumination and noise are rippling through ecosystems.
In his invited essay for Seed Magazine, he notes:

"When their generation looked up at the night sky a century ago, they saw swathes of stars. Today, however, our most familiar starry image may be satellites and astronauts looking down, observing the lights on Earth at night ...

I wonder if some of the changes experts attribute to carbon dioxide and global warming may owe more to nocturnal photons and their associates"

"... humans are adding about three decibels more sound to the ocean each decade, roughly doubling the power of the added noise. Because sound spreads widely in the oceans, human clamor touches every corner. ...As I wonder about life in a darker night, I wonder about marine life in a quieter ocean."

Source: http://seed2.com/54295

Small worlds

Here's a beautiful gallery of microscope photography, including diatoms (plankton with glass-like silica shells ... taken using darkfield and polarised light photography).

Source: http://www.newscientist.com/gallery/dn14971-small-world-gallery

Virgin Birth by Shark Confirmed

Scientists have confirmed the second-ever case of a “virgin birth” in a shark, indicating once again that female sharks can reproduce without mating and raising the possibility that many female sharks have this incredible capacity.
Shark scientist, Dr. Demian Chapman, and his collaborators, have proven through DNA testing that the offspring of a female blacktip shark named “Tidbit” contained no genetic material from a father.

Source: http://www.sciencedaily.com/releases/2008/10/081010173054.htm