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Hello again, Mercury. This week in a trio of papers Science, the scientists behind the Messenger probe released their findings from the craft’s third and final flyby of the planet closest to the sun, which it executed last September. Mercury, they’ve shown once again, is full of surprises—and they’ll get the chance to explore them when Messenger returns and finally enters Mercury’s orbit in March 2011.

Scientists have now mapped 98 percent of the planet by combining the new observations with the first two flybys in January and October 2008, plus the Mariner 10 mission in the ’70s, [said Brett Denevi, coauthor of one of the papers]. The latest flyby filled in a 360-mile-wide gap that had never been imaged before.

“It wasn’t a huge amount of real estate, but there was a lot of really interesting stuff there,” Denevi said. The most exciting features include a 180-mile-wide basin filled with hardened lava, and a crooked bowl surrounded by glass and magma that may be the largest volcanic vent ever identified on Mercury. Together, these features suggest that Mercury had active volcanoes later in its history than scientists had suspected [Wired.com].

The first image above shows a smooth basin dubbed Rachmaninoff, which is one of the smoothest regions seen on Mercury—so smooth that it must have formed from volcanic material in the last billion years or so. The yellowish part in the upper right of this false color image is that volcanic vent.

Louise Prockter, one of the scientists on the volcanism paper, says the findings suggest a Mercury that was active longer than most scientists thought—perhaps up to one to two billion years ago.

“Until MESSENGER, we had expected Mercury to get rid of all its heat early on in its history because it’s pretty small,” Prockter said. “We’ll want to see if the volcanism we see with this basin was an isolated case or whether it was widespread across the surface, which would have us perhaps rethinking our models of Mercury. It seems that Mercury did not get rid of her heat nearly as efficiently as had previously been thought” [Space.com].

That’s not all. Mercury, the researchers found, also releases fierce magnetic storms.

The September MESSENGER flyby is the first time scientists have documented the buildup of magnetic energy in Mercury’s magnetotail, the magnetic lines of force that form a region shaped like a comet’s tail on the planet’s night side. The magnetotail absorbed 10 times more magnetic energy from the sun than Earth’s magnetotail does. It then dumped that energy in just two to three minutes, compared to two to three hours for Earth’s field [Science News].

Now, the waiting is the hardest part. The countdown to Messenger’s big adventure in March stands at eight months.

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Images: NASA/JPL/Johns Hopkins

The Benguela region, off the coast of Namibia, is a shadow of its former self. In the first half of the 20^th century, it was one of the world’s most productive ocean areas and supported a thriving fishing community. Today, the plentiful stocks of sardines and anchovies, and the industries that overexploited them, are gone. The water is choked of oxygen and swarming with jellyfish. Plumes of toxic gas frequently erupt from the ocean floor. But one fish, the bearded goby, is positively thriving in this inhospitable ecosystem. It’s a critical link in a food web that’s on the verge of collapse.

For every tonne of fish currently swimming in the Benguela waters, there are more than three tonnes of jellyfish. Some scientists have suggested that the jellyfish explosion has trapped the region in a “trophic dead-end”. Jellyfish have few predators so, having skyrocketed, their numbers are unlikely to fall back to levels where fish can return.

Below the zone where the jellyfish live, there is a layer that is completely devoid of life, extending from the bottom to around 20-60 metres above it. The mud and sediment along the Benguela ocean floor is extremely low in oxygen (hypoxic), and dominated by algae and large mats of bacteria. It frequently releases massive amounts of toxic gases, like methane and hydrogen sulphide, into the waters above with disastrous consequences for marine life.

But Anne Utne-Palm has found cause for hope. The bearded goby is tough enough to endure in conditions that have driven away most other fish and it’s one of the few species with a strong presence in Benguela. The goby’s success is a bit of a mystery since it’s now the main target for predatory birds, mammals and fish, following the loss of the sardines. And yet, despite being snapped at by hungry beaks and jaws, its population is growing. Now, Utne-Palm has found out why.

The goby lives its life at either ends of the Benguela dead zone and it has very strange inclinations. It spends its days resting on, or hiding inside, the hypoxic mud and it actually prefers these sediments over more typical sand. If another fish did the same, its metabolism would grind to a halt because of the lack of oxygen and the toxic concentrations of hydrogen sulphide. It would become sluggish and vulnerable to predators, and its heart would become irrevocably damaged after a short span of time.

But the goby doesn’t suffer any of these consequences. Its tolerance for low oxygen levels surpasses that of any other bony fish, and it can generate energy aerobically with so little oxygen that the conditions within the Benguela mud are no challenge for it. It’s virtually unaffected by high concentrations of hydrogen sulphide. And even if it’s kept in hypoxic conditions, below its critical threshold, it remains alert and its heart recovers quickly afterwards.

During the evening, the goby rises up to the mid-level waters before sinking back in the early morning. It spends the intervening hours in the company of two species of large jellyfish that rule these waters. And again, it will actually opt to spend time in a chamber with jellyfish, when given the option to swim in an empty tank. By analysing the contents of the gobies’ stomach, and the chemical content of their flesh, Utne-Palm found that the fish actually eats the jellies, which comprise up to 60% of its diet.

Whether it actually hunts live jellies is unclear. Other items in the goby’s stomach, including bottom-dwelling worms and algae, suggest that it probably scavenges upon dead jellies that sink to the ocean floor. Its fondness for loitering among the living jellies might be a way of protecting it from predators like mackerel, which shun the swarm of tentacles.

Rising above the dead zone might have other benefits too. It might help their digestion, which tends to be suppressed in hypoxic conditions. Utne-Palm noted that the gobies’ stomachs are far fuller, and their meals more intact, when they rise to the surface than when they return to the bottom. The waters of the open ocean are also richer in oxygen, allowing the goby to replenish its supply before sinking back to hypoxic levels.

While some species have suffered from the ashes of Benguela’s decline, the bearded goby has the right adaptations to make the most of this almost post-apocalyptic landscape. And it now plays a pivotal role in this brave new world. By eating jellyfish and algae in the hypoxic mud, it transfers some of these dead-end resources back into the food web.

Reference: Science http://dx.doi.org/10.1126/science.1190708

More on fishing:

• Overfishing gives toxic seaweeds an edge in their competition with corals
• Restoring predator numbers by culling their prey
• Human-induced evolution reverses for shrunken fish once fishing stops
• Shark-hunting harms animals at bottom of the food chain
• Fishing bans protect coral reefs from devastating predatory starfish

If the citation link isn’t working, read why here

Imagine enough forest to cover the state of Florida. According to a recent report (pdf), a downturn in illegal logging has protected that amount of forest land–some 42 million acres–over the past decade.

The decrease is a good start, London think tank Chatam House authors say, but there is still more work to do.

“We’re a quarter of the way there,” said Sam Lawson, one of the report’s authors. He expressed the hope that newer regulations–such as a European law passed last week that will ban the import of illegal timber by 2012–would cut the amount of illegal logging even further. [AP]

During the last decade, the report says, Cameroon, the Brazilian Amazon, and Indonesia have decreased logging between 50 and 75 percent. Meanwhile, the seven studied consumer and processing countries have decreased illegally harvested wood imports by 30 percent.

Among those importing countries is the United States, which in 2008 became the first country to ban all imports of illegally logged plants and plant products, including furniture and paper. Europe’s ban, passed earlier this month, will go into effect in 2012.

Still, despite these laws and others in exporting countries, a good deal of illegally sourced lumber still makes it to market. Some exporting countries, like Ghana and Malaysia, haven’t reduced their output, and “processing countries” like China and Vietnam can allow illegal lumber to pass through. Finally, even in the United States some importers don’t abide by the ban.

[C]ompanies still often turn a blind eye, “prioritizing profits over ethical standards,” according to the report’s lead author, Sam Lawson…. But even a total end to illegal timber imports wouldn’t solve the problem, as the contraband would likely find its way to “less sensitive” markets, such as the Middle East, according to Lawson. “If the United States just shuts off its market—even if it could—it would still be a great problem,” he says. [Nature News]

The reports’ authors also outline the consequences if the current illegal harvest does not stop. The report cites the amount of money lost to illegal logging and also logging’s environmental consequences–it estimates that forest destruction is responsible for up to 20 percent of the carbon dioxide emissions caused by human activities.

As a specific example, the report estimates that the 42 million acres mentioned above store 1.2 billion tons of Co2 and are worth 6.5 billion dollars (if harvested legally). The forests’ also serve as home and livelihood for many of these producer countries’ people.

The stakes are high, said lead author Sam Lawson. “Up to a billion of the world’s poorest people are dependent on forests, and reductions in illegal logging are helping to protect their livelihoods,” he said. [AFP]

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Image: flickr / Nirudha Perera