Tuesday, October 29, 2013
US Navy Testing Anti-torpedo Missile
The Navy is gearing up for the deployment and a new round of tests of its Surface Ship Torpedo Defense System — a high tech system designed to protect aircraft carriers by locating, tracking and intercepting incoming torpedoes, Navy leaders said Oct. 24 at the Naval Submarine League, Falls Church, Va.
The upcoming tests, slated to take place on the USS George H.W. Bush, are designed as a follow on to initial end-to-end testing of an early prototype model aboard the Bush this past May. The Navy plans to equip all aircraft carriers with SSTD by 2035.
The SSTD system, which consists of a sensor, processor and small interceptor missile, is a first-of-its-kind “hard kill” countermeasure for ships and carriers designed to defeat torpedoes, said Rear Adm. Dave Johnson, Program Executive Officer, Submarines.
The SSTD is slated for additional testing on board the USS Bush later this month in what’s called a Quick Reaction Assessment, Johnson said. The SSTD will be an Engineering Development Model of the technology, meaning it will be further tweaked and refined before deploying aboard the USS Bush in the near future.
link.
Korea Aerospace Industries Pushes for Changes to KF-X Program
Korea Aerospace Industries (KAI) is pushing for South Korea to cut the technical challenges of its proposed KF-X fighter program, offering a single-engine concept that probably has a distant connection with the Lockheed Martin F-16. KAI's KFX-E design should be cheaper to develop and build than the larger proposals put forward by the Agency for Defense Development (ADD), the chief proponent of the KF-X.link.
Also much smaller than and more differentiated from the Lockheed Martin F-35, the KFX-E may offer the further advantage of minimizing competition from that U.S. stealth fighter. But it may have Lockheed Martin or other U.S. intellectual property in its design, exposing it to a foreign veto over sales or even development.
Seoul will probably have a foreign alternative to consider, too. Western proposals for KF-X include twin-tail developments of the F-16 and Eurofighter Typhoon, and an advanced version of the Boeing F/A-18E/F Super Hornet. Those offerings were included as technology transfer in bids for the separate F-X Phase 3 program for 60 fighters. F-X Phase 3 has been abandoned, but a successor competition will be needed, probably reviving foreign KF-X proposals.
KAI has moved from cooperation to competition with ADD. For a decade, the manufacturer was a design contractor in support of the agency. But industry officials say that at least some KAI executives have long regarded ADD's plan to develop a twin-engine Typhoon-size KF-X as too ambitious. Meanwhile, the South Korean government has repeatedly deferred launching the KF-X. If it goes ahead, it cannot enter service before the mid-2020s. Cutting costs by accepting a smaller size would probably improve the program's chances.
In July, KAI coyly published a picture of a stealthy KF-X concept related to its T-50 supersonic trainer and called KFX-E (or KF-X-E). It gave no details then and did not respond to Aviation Week's request for comment (AW&ST July 22, p. 33). But now the company has stepped up to make its case for the aircraft, arguing at an official seminar that the KFX-E would meet all air force requirements, except for being powered by just one engine.
The KFX-E turns out to be much larger than the T-50, with an empty weight of 9.3 metric tons. It is larger even than the 8.9-ton F-16, from which the T-50 is derived, but remains much smaller than ADD's two proposals, the C103 and C203, each about 11 tons empty (AW&ST April 29, p. 46).
KAI has worked out two versions of the KFX-E, one with a single fin and one with two, the latter presumably demanding more development work but reducing radar reflections. KAI has not provided for a weapons bay in the KFX-E; ADD has reserved space for a bay in its designs, though neither the C103 nor C203 would initially have one. Following a 2009 decision to downgrade the stealthiness of the KF-X, the ADD proposed first to field an aircraft whose shape would give it the makings of a low-observable fighter. Later versions would introduce features to realize that potential.
Attempt no Landings Here: Does Europa Have Penitentes Guarding its Equator?
A deadly bed of icy javelins could be awaiting any spacecraft that tries to land on some parts of the ice-covered world Europa, say researchers who have carefully modeled the ice processes at work on parts of the Jovian moon to detect features beyond the current low resolution images.
If the prediction of long vertical blades of ice is correct, it will not only help engineers design a lander to tame or avoid the sabers, but also help explain a couple of nagging mysteries about the strange moon.
Currently, the very best images of Europa only see 10 meters per pixel, at best, said Daniel Hobley of the University of Colorado. That means that if giant ice daggers do exist, they could still be several meters long and still escape detection.
To learn more, Hobley and his colleagues looked to Chile, where high in the mountains there are peculiar icy features called penitentes that are not found in polar regions.
"Penitentes are very, very sharp blades and spikes of ice," said Hobley. "They are famously well developed in Chile and only develop in the tropics on Earth."
The reason for the tropical location is that in order to sculpt the blade, the sun's rays must shine down almost vertically throughout the year so the light is always drilling down at the bottom of the crevices, between the blades, rather than the sides of the blades. In contrast, at higher latitudes the sun's angle changes dramatically through even a single season, so that light would shine on the sides of the blades and melt them before they had time to develop to any significant size.
The researchers also predict that penitentes, perhaps up to five meters long, could crowd Europa's surface in a wide band centered on the equator.
link.
Sensitivity of Biosignatures on Earth-like Planets orbiting in the Habitable Zone of Cool M-Dwarf Stars to varying Stellar UV Radiation and Surface Biomass Emissions
Authors:
Grenfell et al
Abstract:
We find that variations in the UV emissions of cool M-dwarf stars have a potentially large impact upon atmospheric biosignatures in simulations of Earth-like exoplanets i.e. planets with Earth's development, and biomass and a molecular nitrogen-oxygen dominated atmosphere. Starting with an assumed black-body stellar emission for an M7 class dwarf star, the stellar UV irradiation was increased stepwise and the resulting climate-photochemical response of the planetary atmosphere was calculated. Results suggest a “Goldilocks” effect with respect to the spectral detection of ozone. At weak UV levels, the ozone column was weak (due to weaker production from the Chapman mechanism) hence its spectral detection was challenging. At strong UV levels, ozone formation is stronger but its associated stratospheric heating leads to a weakening in temperature gradients between the stratosphere and troposphere, which results in weakened spectral bands. Also, increased UV levels can lead to enhanced abundances of hydrogen oxides which oppose the ozone formation effect. At intermediate UV (i.e. with x10 the stellar UV radiative flux of black body Planck curves corresponding to spectral class M7) the conditions are “just right” for spectral detection. Results suggest that the planetary O3 profile is sensitive to the UV output of the star from ∼(200–350) nm.We also investigated the effect of increasing the top-of-atmosphere incoming Lyman-α radiation but this had only a minimal effect on the biosignatures since it was efficiently absorbed in the uppermost planetary atmospheric layer, mainly by abundant methane. Earlier studies have suggested that the planetary methane is an important stratospheric heater which critically affects the vertical temperature gradient, hence the strength of spectral emission bands. We therefore varied methane and nitrous oxide biomass emissions, finding e.g. that a lowering in methane emissions by x100 compared with the Earth can influence temperature hence have a significant effect on biosignature spectral bands such as those of nitrous oxide. Our work emphasizes the need for future missions to characterize the UVof cool M-dwarf stars in order to understand potential biosignature signals.
Increased Understanding of the Orbits of Multi Exoplanet Systems
DISK-PLANETS INTERACTIONS AND THE DIVERSITY OF PERIOD RATIOS IN KEPLER'S MULTI-PLANETARY SYSTEMS
Authors:
Clement Baruteau and John C. B. Papaloizou
Abstract:
The Kepler mission is dramatically increasing the number of planets known in multi-planetary systems. Many adjacent planets have orbital period ratios near resonant values, with a tendency to be larger than required for exact first-order mean-motion resonances. This feature has been shown to be a natural outcome of orbital circularization of resonant planetary pairs due to star-planet tidal interactions. However, this feature holds in multi-planetary systems with periods longer than 10 days, in which tidal circularization is unlikely to provide efficient divergent evolution of the planets' orbits to explain these orbital period ratios. Gravitational interactions between planets and their parent protoplanetary disk may instead provide efficient divergent evolution. For a planet pair embedded in a disk, we show that interactions between a planet and the wake of its companion can reverse convergent migration and significantly increase the period ratio from a near-resonant value. Divergent evolution due to wake-planet interactions is particularly efficient when at least one of the planets opens a partial gap around its orbit. This mechanism could help account for the diversity of period ratios in Kepler's multiple systems from super-Earth to sub-Jovian planets with periods greater than about 10 days. Diversity is also expected for pairs of planets massive enough to merge their gap. The efficiency of wake-planet interactions is then much reduced, but convergent migration may stall with a variety of period ratios depending on the density structure in the common gap. This is illustrated for the Kepler-46 system, for which we reproduce the period ratio of Kepler-46b and c.
Paleoecology of Azhdarchid Pterosaurs: Giant Pelicans or Theropod Competitors
Apex predators from ecosystems containing giant azhdarchids to scale with a giant azhdarchid
species, A, the largest known tyrannosaurid, Tyrannosaurus rex from North America, contemporary
of Quetzalcoatlus northropi and other large azhdarchids; B, the small Haţeg dromaeosaur Balaur
bondoc, contemporary of Hatzegopteryx thambema;. C, the 10 m wingspan Arambourgiania
philadelphiae (note that H. thambema was proportionally more robust than Arambourgiania); D,
Homo sapiens, standing height of 1.83 m. {two column width}
Azhdarchid pterosaurs: water-trawling pelican mimics or "terrestrial stalkers"?
Authors:
Mark P. Witton and Darren Naish
Abstract:
The lifestyles of all pterosaurs are contentious, but those of the pterodactyloid clade Azhdarchidae are particularly debated. A 2008 review of the functional morphology of azhdarchid pterosaurs concluded that they were probably terrestrial foragers, as evidenced by their long limbs, generalised skull construction, the arthrological limitations of their cervical series, trackway data indicating terrestrial proficiency, a strong continental skew in the depositional context of their fossils, and several additional lines of corroborating evidence. This hypothesis was recently challenged on three counts: 1) azhdarchid fossils routinely occur in aquatic deposits; 2) terrestrially-foraging pterosaurs were highly vulnerable to predation and 3), aerial ‘water trawling’, where the mandible is pulled though water to catch food in a distended throat pouch, is a more likely foraging strategy. Pelican-like jaw mechanics were suggested for azhdarchids because of the asymmetrical jaw joints in these pterosaurs, which permit lateral deflection of the mandibular rami during jaw extension. We evaluate these three claims and conclude that all are flawed. The frequent occurrence of azhdarchid fossils in aquatic sedimentary systems is not significant with regard to ecology or behaviour, since these provide the overwhelming mechanism for the preservation of all fossil terrestrial animals. Likely pterosaur takeoff abilities and the ubiquitous nature of modern, terrestrially-foraging birds indicate that predation risks on ground-foraging pterosaurs are probably overstated. The kinematics of pterosaur jaws are entirely different to those of pelicans, which are highly specialised compared to those of all other tetrapods, and there are no indications from azhdarchid jaw anatomy that azhdarchids indulged in pelican-like foraging behaviour. The estimated amount of jaw expansion present in azhdarchids was minimal compared to that of pelicans, even when the asymmetrical jaw joints of azhdarchids are taken into account. Moreover, the widespread occurrence of asymmetrical jaw joints in other reptiles demonstrates that they are not related to any specific feeding habits. We conclude that terrestrial foraging remains the most parsimonious habit for azhdarchid pterosaurs.
Mark also has an awesome post up on his own blog on the paper.
Amber Isotope Ratios Give Much Lower Atmospheric Oxygen Levels Since Triassic Than Other Proxies
Stable carbon isotopes of C3 plant resins and ambers record changes in atmospheric oxygen since the Triassic
Authors:
Tappert et al.
Abstract:
Estimating the partial pressure of atmospheric oxygen (pO2) in the geological past has been challenging because of the lack of reliable proxies. Here we develop a technique to estimate paleo-pO2 using the stable carbon isotope composition (δ13C) of plant resins—including amber, copal, and resinite—from a wide range of localities and ages (Triassic to modern). Plant resins are particularly suitable as proxies because their highly cross-linked terpenoid structures allow the preservation of pristine δ13C signatures over geological timescales. The distribution of δ13C values of modern resins (n = 126) indicates that (a) resin-producing plant families generally have a similar fractionation behavior during resin biosynthesis, and (b) the fractionation observed in resins is similar to that of bulk plant matter. Resins exhibit a natural variability in δ13C of around 8‰ (δ13C range: −31‰ to −23‰, mean: −27‰), which is caused by local environmental and ecological factors (e.g., water availability, water composition, light exposure, temperature, nutrient availability). To minimize the effects of local conditions and to determine long-term changes in the δ13C of resins, we used mean δ13C values (View the MathML source) for each geological resin deposit. Fossil resins (n = 412) are generally enriched in 13C compared to their modern counterparts, with shifts in View the MathML source of up to 6‰. These isotopic shifts follow distinctive trends through time, which are unrelated to post-depositional processes including polymerization and diagenesis. The most enriched fossil resin samples, with a View the MathML source between −22‰ and −21‰, formed during the Triassic, the mid-Cretaceous, and the early Eocene. Experimental evidence and theoretical considerations suggest that neither change in pCO2 nor in the δ13C of atmospheric CO2 can account for the observed shifts in View the MathML source. The fractionation of 13C in resin-producing plants (Δ13C), instead, is primarily influenced by atmospheric pO2, with more fractionation occurring at higher pO2. The enriched View the MathML source values suggest that atmospheric pO2 during most of the Mesozoic and Cenozoic was considerably lower (pO2 = 10–20%) than today (pO2 = 21%). In addition, a correlation between the View the MathML source and the marine δ18O record implies that pO2, pCO2, and global temperatures were inversely linked, which suggests that intervals of low pO2 were generally accompanied by high pCO2 and elevated global temperatures. Intervals with the lowest inferred pO2, including the mid-Cretaceous and the early Eocene, were preceded by large-scale volcanism during the emplacement of large igneous provinces (LIPs). This suggests that the influx of mantle-derived volcanic CO2 triggered an initial phase of warming, which led to an increase in oxidative weathering, thereby further increasing greenhouse forcing. This process resulted in the rapid decline of atmospheric pO2 during the mid-Cretaceous and the early Eocene greenhouse periods. After the cessation in LIP volcanism and the decrease in oxidative weathering rates, atmospheric pO2 levels continuously increased over tens of millions of years, whereas CO2 levels and temperatures continuously declined. These findings suggest that atmospheric pO2 had a considerable impact on the evolution of the climate on Earth, and that the δ13C of fossil resins can be used as a novel tool to assess the changes of atmospheric compositions since the emergence of resin-producing plants in the Paleozoic.
New Data From Congo Carton Suggests Greenhouse Paleoclimate During Break up of Rodinia
Depositional age, provenance, and tectonic and paleoclimatic settings of the late Mesoproterozoic–middle Neoproterozoic Mbuji-Mayi Supergroup, Democratic Republic of Congo
Authors:
Delpomdor et al.
Abstract:
The late Mesoproterozoic–middle Neoproterozoic period (ca. 1300 Ma–800 Ma) heralded extraordinary climatic and biological changes related to the tectonic changes that resulted in the assembly (~ 1.0 Ga) and the break-up of Rodinia (880 Ma–850 Ma). In the Democratic Republic of Congo, these changes are recorded in the Mbuji-Mayi Supergroup which was deposited in the SE–NW trending siliciclastic-carbonate failed-rift Sankuru-Mbuji-Mayi-Lomami-Lovoy Basin. New LA-ICP–MS U–Pb laser ablation data on detrital zircon grains retrieved from the lower arenaceous-pelitic sequence (BI group) together with C and Sr isotopic data on carbonates from the upper dolomitic-pelitic sequence (BII group) and an 40Ar/39Ar age determination on a dolerite give a new depositional time frame between 1174 ± 22 Ma and ca. 800 Ma for the Mbuji-Mayi Supergroup. The upper age limit is based on the assumption that the transition between the BIIb and BIIc subgroups recorded the Bitter Springs anomaly. In terms of tectonic and paleoclimatic settings, the BII group was deposited in the eastern passive margin of the Congo Craton during warm periods interlaced with temporarily dry and wet seasons, suggesting greenhouse conditions during the fragmentation of Rodinia.
Chinese Pursuing its own E-2 Carrier Borne AWACS
China’s building a second aircraft carrier—a bigger, more capable flattop to take over from Liaoning, a refurbished Russian vessel that Beijing is using to learn naval aviation fundamentals.
And the new carrier could have a powerful new radar plane, thanks to China’s efforts to copy—and steal—details of the America’s own E-2 Hawkeye early-warning aircraft.
In late October, authorities in Taipei revealed that a major in the Taiwanese air force—part of a ring of up to 20 turncoats—had been caught trying to sell technical data on the E-2 to Chinese agents. Taiwan operates six of the twin-engine E-2s, which feature a large rotating radar dish atop their fuselages for detecting ships and airplanes hundreds of miles away.
Taiwan flies its Hawkeyes from land, but the U.S. and French navies use their own E-2s aboard aircraft carriers. The Northrop Grumman-built radar planes are among the most important aircraft on a flattop. Crewed by “battle managers,” they spot targets and help plot courses for jet fighters and other planes.
Rugged, compact and optimized for short takeoffs and landings, the E-2 is ideal for shipboard use. But it requires a catapult to boost it off a carrier’s deck. China’s rebuilt first flattop Liaoning does not have a catapult and therefore cannot operate large, heavy planes like the Hawkeye. But the second carrier, currently under construction, does have a catapult—if a few blurry photos are any indication.
link.
Monday, October 28, 2013
Sierra Nevada's DreamChaser Suffers Mishap From Failed Landing Gear, Causes DC to Flip
[Yesterday], Sierra Nevada Corporation (SNC) performed its first free-flight approach-and-landing test of the Dream Chaserspacecraft. The vehicle successfully released from its carrier aircraft, an Erickson Air-Crane helicopter, as planned at approximately 11:10 a.m. Pacific Standard [sic] Time. Following release, the Dream Chaser spacecraft automated flight control system gently steered the vehicle to its intended glide slope. The vehicle adhered to the design flight trajectory throughout the flight profile. Less than a minute later, Dream Chaser smoothly flared and touched down on Edwards Air Force Base’s Runway 22L right on centerline. While there was an anomaly with the left landing gear deployment, the high-quality flight and telemetry data throughout all phases of the approach-and-landing test will allow SNC teams to continue to refine their spacecraft design. SNC and NASA Dryden are currently reviewing the data.
link.
Northrop Grumman Playing Chess with Bomber Bid? Or Poker?
Northrop Grumman is not saying whether it will compete in the U.S. Air Force’s Long-Range Strike – Bomber program.link.
Boeing and Lockheed Martin have announced that they will be teaming up to pursue the contract, with Boeing as prime and Lockheed as chief teammate.
“Northrop Grumman views the Long-Range Strike Bomber program as vital to both national security and the power projection capability of the U.S. Air Force,” the company stated. “We do not comment on other companies’ business arrangements and have no further comment on the program at this time.”
The move is surprising, because Northrop has been publicly promoting its qualifications to build the Air Force’s next bomber for more than a decade, based on its experience with the B-2 program. The company continued that campaign through September’s Air Force Association show via advertising and the release of a specially commissioned book about the B-2’s history. But the defense manufacturer elected to no-bid the final stage of the USAF tanker program after investing many years and a great deal of money into its Airbus A330-based proposal.
Even a threat of a no-bid decision puts the Pentagon in an awkward position, because it would turn a program valued at well above $60 billion into a sole-source Boeing effort – which would likely draw widespread scrutiny and some outright opposition in Congress.
One observer notes that Northrop Grumman may be pressuring the Pentagon into more generous funding. The Pentagon is proposing a development program in which cost-reimbursable line items (that is, non-fixed-price) would be limited to areas where the government sees risk, while incentive payments will be tied to tangible deliverables rather than paper milestones. Senior Pentagon leadership expects to supervise a “should cost” process, controlling the release money to the program office.
Alternatively, Northrop Grumman may be looking to level the playing field if – as has been reported – Lockheed Martin is already building an LRS-B-related demonstrator. This would be a replay of the early history of stealth, where Northrop (in 1979) initially declined to bid on what became the B-2 until it was sure that the requirements would not favor Lockheed, which had already flown the Have Blue stealth prototype and was under contract for the F-117.
Total Carbon Input to Eocene Hyperthermal Might Have been 66% Higher Than Previously Thought
Recovering the true size of an Eocene hyperthermal from the marine sedimentary record
Authors:
Sandra Kirtland Turner and Andy Ridgwell
Abstract:
Hyperthermals − episodes of abrupt global warming associated with the massive injection of carbon into the oceans and atmosphere − represent possible analogs for future climate change. However, uncertainties in their magnitude, rate, and duration arising as a result of mixing processes and changes in carbonate preservation as the sediment record is formed, complicate their use in constraining climate sensitivity and the role of carbon cycle feedbacks. Here, we use cGENIE, an Earth system model of intermediate complexity, to assess likely magnitude and rate of carbon input, taking a small hyperthermal event from the early-middle Eocene, C22nH3 (~49.2 Ma) as a case study. We develop an iterative method combined with a sediment model simulating the formation and mixing of deep-sea sediments to converge on an estimate for the ‘true’ magnitude of the carbon cycle perturbation in the atmosphere and ocean that drives the event. In inverting the -0.95‰ benthic δ13C excursion recorded at ODP Site 1258 we obtain an estimate of at least -1.45‰ for the atmospheric CO2 δ13C excursion that drove event C22nH3. We also assess controls on inter-site variation of event shape in model sediments and find that sedimentation rate is the strongest determinant of modeled event size, with higher sedimentation rate sites recording the atmospheric signal more accurately. Our revised estimate for the size of C22nH3 implies a total carbon input almost two thirds higher than would be deduced if the recorded δ13C excursion magnitude was taken at face value.
Carbon Rich Terrestrial Worlds may be Water Poor, Lack Oceans
Planets rich in carbon, including so-called diamond planets, may lack oceans, according to NASA-funded theoretical research.link.
Our sun is a carbon-poor star, and as result, our planet Earth is made up largely of silicates, not carbon. Stars with much more carbon than the sun, on the other hand, are predicted to make planets chock full of carbon, and perhaps even layers of diamond.
By modeling the ingredients in these carbon-based planetary systems, the scientists determined they lack icy water reservoirs thought to supply planets with oceans.
"The building blocks that went into making our oceans are the icy asteroids and comets," said Torrence Johnson of NASA's Jet Propulsion Laboratory in Pasadena, Calif, who presented the results Oct. 7 at the American Astronomical Society Division of Planetary Sciences meeting in Denver. Johnson, a team member of several NASA planetary missions, including Galileo, Voyager and Cassini, has spent decades studying the planets in our own solar system.
"If we keep track of these building blocks, we find that planets around carbon-rich stars come up dry," he said.
Johnson and his colleagues say the extra carbon in developing star systems would snag the oxygen, preventing it from forming water.
"It's ironic that if carbon, the main element of life, becomes too abundant, it will steal away the oxygen that would have made water, the solvent essential to life as we know it," said Jonathan Lunine of Cornell University, Ithaca, N.Y., a collaborator on the research.
paper link.
hat tip to James.
HAT-P-13 system Exoplanets may be Apsidally Locked
SECULAR ORBITAL EVOLUTION OF COMPACT PLANET SYSTEMS
Authors:
Ke Zhang, Douglas P. Hamilton, and Soko Matsumura
Abstract:
Recent observations have shown that at least some close-in exoplanets maintain eccentric orbits despite tidal circularization timescales that are typically much shorter than stellar ages. We explore gravitational interactions with a more distant planetary companion as a possible cause of these unexpected non-zero eccentricities. For simplicity, we focus on the evolution of a planar two-planet system subject to slow eccentricity damping and provide an intuitive interpretation of the resulting long-term orbital evolution. We show that dissipation shifts the two normal eigenmode frequencies and eccentricity ratios of the standard secular theory slightly, and we confirm that each mode decays at its own rate. Tidal damping of the eccentricities drives orbits to transition relatively quickly between periods of pericenter circulation and libration, and the planetary system settles into a locked state in which the pericenters are nearly aligned or nearly anti-aligned. Once in the locked state, the eccentricities of the two orbits decrease very slowly because of tides rather than at the much more rapid single-planet rate, and thus eccentric orbits, even for close-in planets, can often survive much longer than the age of the system. Assuming that an observed close-in planet on an elliptical orbit is apsidally locked to a more distant, and perhaps unseen companion, we provide a constraint on the mass, semi-major axis, and eccentricity of the companion. We find that the observed two-planet system HAT-P-13 might be in just such an apsidally locked state, with parameters that obey our constraint reasonably well. We also survey close-in single planets, some with and some without an indication of an outer companion. None of the dozen systems that we investigate provides compelling evidence for unseen companions. Instead, we suspect that (1) orbits are in fact circular, (2) tidal damping rates are much slower than we have assumed, or (3) a recent event has excited these eccentricities. Our method should prove useful for interpreting the results of both current and future planet searches.
Dinosaur Cove Site in Albanian Cretaceous Australia Has Landing Trackways From Flying Birds
Two fossilized footprints found at Dinosaur Cove in Victoria, Australia, were likely made by birds during the Early Cretaceous, making them the oldest known bird tracks in Australia.
The journal Palaeontology is publishing an analysis of the footprints led by Anthony Martin, a paleontologist at Emory University in Atlanta who specializes in trace fossils, which include tracks, burrows and nests. The study was co-authored by Patricia Vickers-Rich and Michael Hall of Monash University in Victoria and Thomas Rich of the Museum Victoria in Melbourne.
Much of the rocky coastal strata of Dinosaur Cove in southern Victoria were formed in river valleys in a polar climate during the Early Cretaceous. A great rift valley formed as the ancient supercontinent Gondwana broke up and Australia separated from Antarctica.
"These tracks are evidence that we had sizeable, flying birds living alongside other kinds of dinosaurs on these polar, river floodplains, about 105 million years ago," Martin says.
The thin-toed tracks in fluvial sandstone were likely made by two individual birds that were about the size of a great egret or a small heron, Martin says. Rear-pointing toes helped distinguish the tracks as avian, as opposed to a third nearby fossil track that was discovered at the same time, made by a non-avian theropod.
A long drag mark on one of the two bird tracks particularly interested Martin.
"I immediately knew what it was – a flight landing track – because I've seen many similar tracks made by egrets and herons on the sandy beaches of Georgia," Martin says.
Martin often leads student field trips to Georgia's coast and barrier islands, where he studies modern-day tracks and other life traces, to help him better identify fossil traces.
The ancient landing track from Australia "has a beautiful skid mark from the back toe dragging in the sand, likely caused as the bird was flapping its wings and coming in for a soft landing," Martin says. Fossils of landing tracks are rare, he adds, and could add to our understanding of the evolution of flight.
link.
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