Found in the northwest province of Xinjiang, the fossil deposit contains the remains of as many as 1,800 turtles.
The fossils were found in April 2008 in China’s Turpan Basin. The region, which is likely China’s hottest and driest, lies below sea level.
“The area is absolutely desolate with almost no green, but a series of oases are nearby that used to serve as stopping posts along the silk road,” Dr. Walter G. Joyce, a paleontologist affiliated with Germany’s University of Tubingen and Yale University, said in an email response to questions.
The fossils are concentrated within an area of less than a hectare in size. A hectare is equal to 10,000 square meters.
“Some of the shells were stacked up on top of one another in the rock,” Joyce said.
A paleontology graduate student working with Wings on a prospecting expedition unexpectedly found the turtle remains.
“Given that the mesa is rather narrow, a colleague decided to check out the other side and was surprised to see turtles litter the surface,” Joyce said.
Researchers removed a half-meter square block of the rock containing a high concentration of the fossils for study off-site. They photographed the individual fossils contained in it and, from the number of individual remains found, determined that the density of specimens within the bone bed is equal to about 36 per square meter.
Joyce explained that a second area of the bone bed has a lower concentration of fossils and that the team estimated the number of individuals in that section by counting the number of shell pieces found in that area.
“What we got at the end is a conservative estimate,” he said. “It is very likely that many more turtles died at the site!”
Joyce added that the specimens are likely to increase the number of known Jurassic turtle individuals by at least two-fold.
During the Jurassic period, which ended about 145 million years ago, the area of Xingjiang in which the fossils were discovered was verdant, with many lakes and rivers.
Scientists are able to infer the climactic conditions of the area tens of millions of decades ago by closing examining the sediments that surround the fossils. The distinctive red sediments in the particular geologic formation in which the fossils were found indicates that, at the time they were laid down, the climate in the area was seasonally arid.
Joyce clarified that the “characteristic assemblage of plant and animal fossils” and “such rarities as the turtle mass grave we found” also give researchers enough information to support that conclusion.
The rock layer that holds the fossils, called the Qigu Formation, includes the remains of freshwater mollusks, which indicates the area was periodically subjected to river flows or under a lake.
The fossils are not scattered throughout the thickness of the Qigu Formation. According to the paper describing the discovery, the depth of the bone bed does not exceed 20 centimeters.
Wings and Joyce, together with their colleagues, therefore concluded that the turtles likely gathered in a dry lake bed to await rain. When the rain fell, it produced a flood that moved the turtles into one place, where sediment buried them.
“We know from modern semi-tropical areas, regions with dry and wet seasons, that aquatic turtles will accumulate in retreating rivers and ponds as droughts progress and often die when these water dry out completely,” Joyce said. “This is particularly typical for Australia, but also seen in parts of Africa, South America, and even Florida.”
The turtles may belong to a previously unknown species.
“We presume we found a new species, but we are not sure yet,” Joyce said.
The fossils date to the middle Jurassic, about 164 million years ago. The oldest known turtle species dates to about 220 million years ago. Turtles have existed on Earth for a period longer than snakes, lizards, or crocodiles.
Joyce said that the find is likely to help paleontologists gain a greater understanding of Mesozoic turtle diversity.
“We know from living organisms that individuals of some species look very similar, whereas individuals of other species show a lot of variation,” he said. “As a paleontologist, it is therefore always difficult to assess if your fossil looks different from others because it is a new species, or because it is part of an already known, but variable species. With data from the new site we will finally be able to more rigorously assess patterns of diversity of turtles in the Jurassic of Asia.”
Wings and Joyce, together with other scientists, conducted further examination of the specimens and surrounding rock layer on-site in April 2009 and October 2011. Their research was published in the Oct. 21 edition of Naturwissenschaften.
Journal reference: Oliver Wings, Márton Rabi, Jörg W. Schneider, Leonie Schwermann, Ge Sun, Chang-Fu Zhou, Walter G. Joyce. An enormous Jurassic turtle bone bed from the Turpan Basin of Xinjiang, China. Naturwissenschaften, 2012. DOI: 10.1007/s00114-012-0974-5.
President Barack H. Obama and his challenger, former Massachusetts governor Willard Mitt Romney, completed their third debate of the 2012 presidential campaign season Monday night without being asked any questions about climate change.
It was a continuation of a pattern that, for the first time since 1988, saw no questions about the phenomenon that threatens to significantly alter Earth’s environment and that is likely to cause huge economic burdens to humanity.
Although not mentioned during the three presidential candidate debates and single vice presidential candidate debate, both Obama and Romney spoke of climate change at their respective parties’ conventions this summer.
Romney said that he is not seeking the presidency to prevent sea level rise or protect the planet’s natural environments, while Obama retorted that “climate change is not a hoax.”
“More droughts and floods and wildfires are not a joke,” he said in Charlotte. “They are a threat to our children’s future.”
The U.S. Department of Defense has listed climate change as among the most significant security threats to the nation, while local impacts within the country could cost the American economy billions of dollars.
Record ice melt in the Arctic this year is among the latest indications that heating of Earth’s atmosphere as a result of industrial emissions continues.
The debates did include discussion of both candidates’ plans to facilitate increased extraction and use of fossil fuels.
This graphic shows you how to orient yourself to find the apparent source of the Orionid meteor shower. Courtesy NASA-JPL
There’s a new planet in the stellar neighborhood next door.
Astronomers said this week that the exoplanet, which is in the triple-star Alpha Centauri system, has a mass comparable to that of Earth. It is the closest exoplanet to Earth yet discovered.
Yale University astronomer Debra Fischer told the New York Times that the find is “the story of the decade.”
“I’d bet $100 that there are other planets that are there as well,” she is quoted as saying in the story published in the Times’ Oct. 16 edition.
While the newly-discovered exoplanet is about the same size as Earth, it would not be a comfortable place for human beings. The planet orbits Alpha Centauri-B, one of the Alpha Centauri system’s three suns, at a distance of about six million kilometers.
That is so close that its surface temperature would exceed 2,000 degrees Fahrenheit.
By comparison, Mercury is about 46 million kilometers from the Sun at its perihelion. The closest planet to the Sun, the daytime surface temperature on Mercury can exceed 800 degrees Fahrenheit.
Astronomers used a technique that involves measuring slight changes in the star’s motion caused by the gravitational pull of an object orbiting the star.
The newly-discovered exoplanet causes only a tiny wobble in the motion of Alpha Centauri-B. According to a press release issued by the European Southern Observatory, the star’s movement is altered by only about 51 centimeters per second.
“Our observations extended over more than four years using the HARPS instrument and have revealed a tiny, but real, signal from a planet orbiting Alpha Centauri B every 3.2 days,” Xavier Dumusque, a researcher at Geneva Observatory in Switzerland and Centro de Astrofisica da Universidade do Porto in Portugal and the lead author of the paper, said. “It’s an extraordinary discovery and it has pushed our technique to the limit.”
Alpha Centauri is located 4.3 light years, or about 25.6 trillion miles, from Earth – a distance that is about 600,000 times farther from our planet than is the Sun.
That means it would not be easy to travel to the newly-discovered planet.
If a spaceship traveling at the maximum velocity achieved by the space shuttles during their missions in Earth orbit, a journey to the Alpha Centauri system would take approximately 165,000 years to complete.
The significance of the planet isn’t limited to its size relative to Earth. It is also the lightest exoplanet among the more than 800 confirmed so far.
Artist’s conception courtesy European Southern Observatory, L. Calcada, Nick Risinger.
If you can get outside and beneath a dark night sky in the wee hours of Sunday morning, the reward might be a chance to see remnants of Halley’s comet.
The annual Orionid meteor shower will peak at 10 pm MDT, but the best viewing of the spectacle will happen in the hours between midnight on Saturday night and dawn on Sunday.
“Halley’s Comet is very much alive and well,” Dr. William J. Cooke, the lead scientist at NASA’s Meteoroid Environment Office, said. “Like all comets, it sheds debris as it approaches the Sun. Ice sublimates to gas, which frees bits of rock to escape the comet’s surface and form streams of material in its wake. Over time, some of these particles will collide with Earth and produce the Orion meteor shower we see now.”
Halley’s comet, which has been observed by humans since 240 BC, was last visible in 1986. It won’t be seen again until 2061.
There’s a bonus to staying up late or waking up before dawn, too. You should be able to see Jupiter to the northeast of Orion. The solar system’s largest planet will be brighter than Sirius.
If you are out close to dawn you can look for Venus in the eastern sky. Earth’s neighbor will be even brighter than Jupiter.
One fun way to enjoy the Orionid meteor shower is to locate the region of the heavens that appears to be its source. You don’t have to do this to see the “shooting stars,” though, since they will appear throughout the sky.
If you want to find the constellation that looks like the fountainhead of the meteors, begin by locating Sirius. Sirius is the brightest star in the night sky and will be to the southwest of the meteor shower’s namesake, Orion.
Once you find Orion, locate the three stars in the middle of the image. They make up Orion’s Belt. The meteors will seem to come from the rectangle that surrounds this region of the constellation.
The Orionids are somewhat unusual in that the number of meteors visible each year is fairly constant.
“This is because the Orionid stream is fairly wide (10 million miles or so) and not concentrated like the Leonids or Perseids,” Cooke said. “Because it is wide, the material is more evenly distributed, which explains the steady rates.”
Cooke noted that the rate of meteors can vary by factor of 3.
“The low is 20 per hour, and rates over 60 per hour have also been observed,” he said. “The past few years have seen Orionid rates on the higher side.”
You can continue to see a dwindling array of shooting stars in the early morning sky through Nov. 14. The Orionids start to appear in early October.
The next significant meteor shower happens in December. The Geminids, which peak around Dec. 12, are even more spectacular than the Orionids.
“It has the best rates of any annual shower, usually topping 100 per hour,” Cooke said.