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NASA's orbiting HiRISE camera captured a Martian mystery

NASA's orbiting HiRISE camera captured a Martian mystery on June 10: What formed the intriguing mounds visible on the floor of a large, ancient crater?

The mounds may be ejecta from meteor impacts, lava laid down by volcanic eruptions, or fluvial sediments from a wetter, ancient Mars.

Although the question remains unanswered, scientists believe that the rough texture of the mounds means that the crater's bedrock surface has been eroded over time, perhaps by whipping Martian winds.

The European Space Agency's Venus Express creeps into closer orbit

The European Space Agency's Venus Express creeps into closer orbit around its host planet in an artist's impression. Maneuvers began last week to steer the craft downward.

When the spacecraft settles in its new orbit on August 4, it will be within 115 miles (185 kilometers) of the planet's surface, a prime position for studying Venus's magnetic fields and ionosphere, the uppermost layer of the atmosphere.

Scientists also hope to determine the density of the Venetian atmosphere by measuring the drag exerted as the probe moves nearer to the planet.

Global Warming Forces Innovative Sea Turtle Protection

The near record hatch, up from just a handful the year before, signaled progress.
Absent from the headlines, however, was the fact the turtles were born in a fenced, shaded hatchery to protect them from predators and scorching sun.

Scientists here and elsewhere are increasingly finding they have no choice but to intervene as a warming Earth, changing ocean conditions, and coastal development threaten to outpace the sea turtles' ability to adapt.

"These are no longer natural problems," said Carlos Drews, who leads the marine turtle program for the World Wildlife Fund in Latin America. "We can't expect the turtles to adjust."

This realization has sparked a growing discussion among conservationists on how to help species cope with climate change.

"It's an experiment we've been forced into, and one we hadn't planned for," said Michael Coyne, director of SeaTurtle.org and chairperson of the International Sea Turtle Society.

Highly Endangered Long-lived animals, leatherback sea turtles can reach 6.5 feet (2 meters) in length and weigh up to 2,000 pounds (900 kilograms).

Found in the Pacific, Atlantic, and Indian Oceans and the Mediterranean Sea, the animals are highly endangered.

The Pacific population, for example, has declined to an estimated 5,000 animals, a 95 percent drop since 1980. Coastal development, poaching, and fishing bycatch are the main culprits.

(Related story: Rare Leatherback Turtles Gain Protection in Costa Rica [March 2008])

With climate change bringing additional burdens, turtles and their habitat must be carefully monitored, Coyne says.

"Sea turtles are … driven by temperature," Coyne said. "We need to track their movements as climate change progresses, then protect their new habitat."

Beaches "Too Hot"

Already close to extinction, climate change may prove the last straw for the Pacific leatherback. Warming temperatures on nesting beaches are the primary concern.

Unlike humans, sea turtles have no sex chromosomes. The temperature of beach sand surrounding an egg determines the sex of a developing turtle.

When temperatures top 85 degrees Fahrenheit (29.4 degrees Celsius), females predominate; under cooler conditions, males take over.

In places like Junquillal, beach sand temperatures inside nests regularly reach a lethal 104 degrees Fahrenheit (40 degrees Celsius), according to biologist Gabriel Francia, who leads a World Wildlife Fund project there.

Surface sand temperatures can be much worse, often cresting at 158 degrees Fahrenheit (70 degrees Celsius).

"If we leave these eggs in the sand to fend for themselves, they hard-boil and die. It is just too hot," Francia said.

Biologists and community members are planting native trees to restore natural vegetation—and shade—to the beach.

With the species at risk, the biologist has no choice but to transplant the nests. He says the few turtles that might hatch would be female, skewing the natural balance of sexes.

"We're tinkering with nature. And we don't know what effect that could have," Coyne said. "Ideally we can find a way to help turtles survive on their own in the long-term."

Only one in a thousand sea turtles is believed to survive the natural and human-made hurdles of life at sea—from hungry sea birds to offshore fishing nets.

Climate change may stack the odds even more for breeding turtles that return decades later to their natal beaches to nest.

"If the turtles return to these beaches and find them flooded, or too warm, we have to ensure that they have someplace else to go," Coyne said.

Ancient feeding patterns and migration routes may also be affected by changing ocean temperatures and rising seas.

Migrating Beaches

James Spotila, a turtle researcher at Drexel University in Philadelphia, Pennsylvania, says defending against such threats starts with protecting ocean beaches and the forest that backs them.

"Beaches can then migrate landward as ocean levels rise, continuing to provide habitat for nesting turtles," Spotila said.

Drews, of the World Wildlife Fund, says the challenge is deciding which beaches to protect.

Seeking refuge from heat, the adaptable turtles could push farther north or south, depending on rainfall and cloud coverage patterns.

"We have to develop a more flexible conservation model if these turtles are to survive. The rigid park boundaries of the past won't do," Drews said.

For now small victories, such as the bumper crop of turtles this year on Playa Junquillal, are a good start, he said.

"We need be sure every egg hatches, every baby leatherback lives, so that populations are best equipped to survive the new challenges they face," Drews said.

Total Solar Eclipse on August 1: Where, How to See It

Solar eclipses have been blamed in the past for war, famine, and the deaths of kings. But the upcoming total eclipse on August 1 will mostly be celebrated by excited skywatchers—even if it won't break any records.

The sun will be completely obscured for just under two and a half minutes, "a tad on the short side," according to astrophysicist Fred Espenak, an eclipse expert based at the NASA Goddard Space Flight Center.

A typical eclipse lasts for three minutes, Espenak said, and the longest possible is seven and a half minutes.

When it starts, this year's full eclipse will be visible from a narrow arc spanning the Northern Hemisphere.

Its path will begin in Canada and continue northeast across Greenland and the Arctic, then southeast through central Russia, Mongolia, and China.

The eclipse will start around 8:30 a.m. Greenwich mean time in the eastern part of the arc, leading to totality in just under an hour.

In a much wider swath of the globe—including northeastern North America along with most of Europe and Asia—people will be able to see a partial eclipse.

"Drop Dead Gorgeous"

The moon crosses between Earth and the sun once a month during the new moon. For an eclipse to happen, the moon has to come directly between the two bodies—it can't be too high or low relative to Earth. (See photos of the full moon from Earth and space.)

Sometimes the moon will be close enough that just an edge will pass in between, resulting in a partial eclipse.

About 25 percent of eclipses are total eclipses, and there are about seven of these a decade, Espenak said. But at any given geographic location, a total eclipse will be visible an average of once in 375 years.

When a total solar eclipse takes place, about half the daytime world doesn't see any of it, Espenak said. Another 49 percent of people see it as a partial eclipse.

Less than one percent of people see totality, which Espenak describes as "drop dead gorgeous."

"On a scale of one to ten, a partial eclipse is of some interest," he said. "A total eclipse on that scale is ten million. It can't be compared to anything else. It should be on everybody's life list."

Of course, the weather can throw a monkey wrench in any observation plans.

This year, conditions in China are likely to be most favorable for getting a good look at the full eclipse, according to weather data analyzed by Espenak and Jay Anderson from the University of Manitoba in Canada.

Their calculations show that the skies above China in August are cloudy around 35 percent of the time, compared with upward of 90 percent of the time in many other parts of the eclipse's path.

"It's always a crapshoot," Espenak said. "You try to stack the odds in your favor."

Pop Tarts and Bad Omens

Tom Burns, director of the Perkins Observatory in Delaware, Ohio, helped put together a viewing-safety Web site during the Christmas eclipse of 2001.

He was hearing too often, he recalled, of people trying to view the partial eclipse through sunglasses, compact discs, or—surprisingly—Pop Tart bags.

"The only time it's safe to observe an eclipse through a Pop Tart bag is if the Pop Tart is still in it," he said.

He and his colleagues, who frequently instruct groups of skygazers on safe sun-watching, instead recommend special eclipse glasses.

Eclipses haven't always been eagerly anticipated, NASA's Espenak added. In ancient times the events were often seen as bad omens.

A total solar eclipse that may be tied to a real event was described in Homer's epic poem The Odyssey as spreading "an evil mist" over the world while suitors courted Odysseus's wife.

And an eclipse viewed in England in A.D. 1133 was seen as portending the death of King Henry I.

Even today, in some places, fears persist.

"A lot of … women believe viewing an eclipse will cause birth defects if they're pregnant," Espenak said. "I've seen this in Mexico, India, Indonesia, Bolivia."

For the growing population of skygazers who would love to see an eclipse and can't make it northward this year, it might be best to make reservations to visit southern Illinois, he added.

Weather permitting, people there will get to see total solar eclipses in 2017 and 2024.

Ice Adrift From Warming Scrapes Antarctic Seabed Bare

Ocean-bottom scrubbings along the West Antarctic Peninsula will increase as temperatures rise, annihilating some animal and plant populations but helping others by clearing the habitat, the study said.

The study establishes for the first time the intimate link between increased scouring and declines in winter sea ice due to climate change, researchers said.

In the past, these icebergs were locked in place by winter sea ice for longer periods and only free to crash into the seabed in summer.

"Our results suggest that as the winter sea ice season shortens, the thousands of icebergs that float around the coastline of the Antarctic Peninsula will be free to move around and collide with the seabed creatures with ever increasing frequency," lead author Daniel Smale of the British Antarctic Survey, said in an e-mail.

A Significant Degree

Antarctica is one of the fastest warming regions in the world, the researchers said.

Sea temperatures around Antarctica tend to be stable, spanning from 28.8 degrees Fahrenheit (-1.8 degrees Celsius) to 35.6 degrees Fahrenheit (2 degrees Celsius).

The Bellingshausen Sea along the western side of the Antarctic Peninsula, however, has seen its temperatures increase by about a degree Celsius in the last 50 years, said marine biologist and study co-author David Barnes, also of the British Antarctic Survey.

"This may not sound like a lot, but it is nearly a third of the total annual variability" for that region of the sea, Barnes said.

The study will be published in tomorrow's issue of the journal Science.

Each winter, a frozen crust called fast ice forms on the sea's surface. It can stretch for thousands of square kilometers but is rarely found more than seven feet (two meters) thick.

The winter ice decays as winter temperatures rise, releasing slabs of iceberg to drift in the sea.

These icebergs can vary dramatically in size—from the size of fists to small countries, Barnes said.

Once freed from the fast ice, icebergs are blown by winds and carried by sea currents until they smash into the seabed in shallow depths.

"They not only kill virtually everything underneath on the seabed—mainly animals—but crush rock and reshape the seabed," Barnes said.

Vulnerable animals include Antarctic worms, sea spiders, and urchins, the scientists said.

(Related photos: "Giant, Unknown Animals Found off Antarctica" [March 28, 2008])

An Unfamiliar Look

Researchers studied the ice scouring over a five-year period, regularly monitoring markers placed at varying depths along the seafloor.

Made of molded concrete and plastic, the markers deformed and splintered when they encountered the force of a drifting iceberg.

The variety in iceberg sizes creates a range of damaged areas on the seafloor, Barnes said.

In shallow waters, researchers measured damaged areas a few meters by a meter. At deeper regions, however, they found impacted areas up to 0.62 mile (a kilometer), he said.

Smale added that icebergs can ground out at depths of up to 550 yards (500 meters), which means much of polar seabed could be susceptible to ice scouring.

The impact is dramatic, Barnes said. "Diving on the big ice scours after they have happened is like visiting a completely new area, everything looks unfamiliar," he said.

Life is able to eventually rebound in the deadly wake of a scrubbing, but the process takes a while, Barnes said.

"Antarctic animals grow very slowly—in fact, they do virtually everything very slowly—so re-colonization is not quick," he said.

Part Biodiversity, Part "Black Pools of Death"

By clearing out the seafloor, however, the scouring also enables a wide range of species to live, Barnes said.

"Think of it like a forest," he said. "The weedy species that are normally crowded out and out-competed by the dominant species persist where big trees fall and create a clearing."

The research can help expand awareness about the impact of warming temperatures, said a marine biologist not affiliated with the study.

"It is a nice story about what sea ice can do to marine life and sediment characteristics on the seafloor, a place where the general public would not associate processes happening on the surface with what is happening on the bottom of the ocean," said Kathleen Conlan at the Canadian Museum of Nature in Ottawa.

Conlan, who has conducted research on ice scouring in the eastern Canadian Arctic, agreed that its effect on marine life could be varied.

In some areas, it can promote diversity, where it turned over nutrient-rich sediments and pushed out dominant grazers, such as sea urchins.

In other locations, however, the result could be catastrophic, "producing black pools of death," she said.

Shrimp-Like Fossil Confirms Antarctica Was Once Warmer

Windswept and frigid, Antarctica's Dry Valleys region is among the most inhospitable on Earth. But it wasn't always that way.

Scientists have discovered the fossil of a 14 million-year-old crustacean lurking in the sediments of an ancient lake. Together with well-preserved mosses, these tiny cousins of shrimp -- called Ostracods -- offer new evidence that the icy continent was once much warmer.

Led by Mark Williams of the University of Leicester in the United Kingdom, a team of researchers sifted through sediments left by the ancient Lake Boreas, looking for signs of Antarctica's climate history. What they found stunned them.

"One of my students working on a microscope said 'could there be little eyes staring back at me?'" Allan Ashworth of North Dakota State University in Fargo said. "I said 'No,'" but further examination proved that's exactly what they were -- Ostracod eyes.

Some 60,000 species of Ostracods thrive today around the planet in both fresh and salt water. The tiny invertebrates are found in places where summer temperatures are as low as 5 degrees Centigrade (41 degrees Fahrenheit). But there are none alive in the Antarctic Dry Valleys, where the austral summer averages between -15 and -20 degrees C (5 to -4 degrees F).

Scientists know that Antarctica used to be much warmer -- fossil leaves from ancient plants have been found to exist up until around 40 million years ago, and pollen has been dated to as early as 20 million years ago.

But how the continent came to be so cold is something of a mystery.

Around 14 million years ago, scientists are fairly certain the climate resembled modern-day Alaska. Within a million years a deep freeze had settled in, and the ice sheets grew to mammoth proportions, where they mostly remain today.

The newly discovered Ostracod fossils confirm that the changes -- which until now had only been observed in ocean floor sediments -- were also playing out on land in Antarctica.

"We've shown that this change in climate had a profound impact on Antarctica," Ashworth said. "The evidence tends to suggest the threshold of temperature was never reached again in that part of Antarctica. We'd argue that it's been locked down and frozen for the past 14 million years."

Timothy Naish of Victoria University of Wellington in New Zealand agreed that the team's study was "important to our understanding of Antarctic climate." But he added that there's still a lot of uncertainty about what happened after the 14-million-year mark.

"We see a lot of variability in climate, and there is evidence that a significant amount of the Antarctic ice sheets melted recently, around three million years ago," before freezing again, Naish told Discovery News.

Gulf Dead Zone Grows Bigger Than Ever

A "dead zone" in the Gulf of Mexico off the Texas-Louisiana coast this year is likely to be the biggest ever and last longer than ever before, with marine life affected for hundreds of miles, a scientist warned.

"It's definitely the worst we've seen in the last five years," said Steve DiMarco, a Texas A&M University professor of oceanography who for 16 years has studied the Gulf of Mexico dead zone, so named because the oxygen-depleted water can kill marine life.

The phenomenon is caused when salt water loses large amounts of oxygen, a condition known as hypoxia that is typically associated with an area off the Louisiana coast at the mouth of the Mississippi River. The fresh water and salt water don't mix well, keeping oxygen from filtering through to the sea bottom, which causes problems for fish, shrimp, crabs and clams.

This year's dead zone has been aggravated by flood runoff from heavy spring rains and additional runoff moving into the Gulf from record floods along the Mississippi.

DiMarco, joined by researchers from Texas A&M and the University of Georgia, just returned from an examination of 74 sites between Terrebonne and Cameron, La. He said the most severe hypoxia levels were recorded in the mid-range depths, between 20 and 30 feet, as well as near the bottom of the sea floor at about 60 feet.

Some of the worst hypoxic levels occurred in the western Gulf toward the state line.

"We saw quite a few areas that had little or no oxygen at all at that site," DiMarco said Tuesday. "This dead zone area is the strongest we've seen since 2004, and it's very likely the worst may be still to come.

"Since most of the water from the Midwest is still making its way down to the Gulf, we believe that wide area of hypoxia will persist through August and likely until September, when it normally ends."

Last year, DiMarco discovered a similar dead zone off the Texas coast where the rain-swollen Brazos River emptied into the Gulf.

The zone off Louisiana reached a record 7,900 square miles in 2002. A recent estimate from the National Oceanic and Atmospheric Administration and Louisiana State University shows the zone, which has been monitored for about 25 years, could exceed 8,800 square miles this year, an area roughly the size of New Jersey.

DiMarco said a tropical storm or hurricane likely would have no impact on this year's zone, believed to be caused by nutrient pollution from fertilizers that empty into rivers and eventually reach the Gulf.

Could a Contact Lens Save Your Vision?

Soon contact lenses won't just correct eyesight; they could save your vision.

By applying electrically conductive, antibiotic nanosilver particles to contact lenses, researchers at the University of California, Davis, can continuously map the pressure inside a human eye while administering medication directly and painlessly into it.

The new lenses promise to advance understanding of diseases like glaucoma, the second leading cause of blindness worldwide, and could save the eyesight of millions, say the researchers.

"It would be really helpful to measure the pressure inside the eye continuously," said Tingrui Pan, a professor at the University of California, Davis, and co-author of a paper describing the lenses in Advanced Functional Materials.

Pressure inside the eye, the leading indication of glaucoma, can vary widely from day to day, even minute to minute. Currently, doctors only measure pressure every few months (depending on the patient), said James Brandt, a physician at UC Davis who is involved in the research.

"Compare that to another chronic disease like diabetes, where we can have blood sugar measurements several times a day," he added.

Right now the contact lenses, made from polydimethylsiloxane (PDMS), are a close cousin to modern-day contact lenses. They have an eight-by-eight grid nanosilver lines that provide 64 pressure points. Each point independently monitors eye pressure and relays information to a computer that records the pressure inside the eye.

Future models could have thousands of points with invisible nanosilver lines.

Medicine to lower the pressure inside the eye could also be loaded into the contact lens. A mild electrical charge, unnoticeable to the wearer, would push the medication into the eye and monitor its effect -- or lack thereof.

Putting medication directly into something that many people have to wear every day could ensure that patients are taking their medication, said Jack Cioffi, editor of the Journal of Glaucoma, who was not involved in the UC Davis research.

"Roughly one-third of all kidney transplant patients go off drugs that could save their lives in less than a year," said Cioffi. "You trust that people are taking the medication, but we would like to ensure that they are compliant, and then see if the drugs are working."

Cioffi notes that other available devices can monitor internal eye pressure, but they require implantation surgery, a risk that the new contact lenses would avoid.

"Overall, this device has good promise because it's clear, can be made into a contact lens, is bio-compatable... and would make for a non-invasive intraocular pressure measuring device," said Cioffi.