Threat of group extinction proves a powerful motivator

Charles Darwin was right: Groups enjoy an advantage whose members are "ready to aid one another and to sacrifice themselves for the common good," according to a new study by researchers at Rice University, Texas A&M University and the University of East Anglia.

Using variations of the public goods game, the researchers showed that when no other mechanism is present to reinforce group cooperation, the threat of group extinction is sufficiently powerful to motivate and increase cooperation within a group.
"The finding is stunning for what it says about group extinction," said Rice Professor Rick Wilson, one of the authors of the paper appeared this week in the journal PLOS ONE. "People respond to threats to their group. They're willing to forego opportunities to free ride on the efforts of their group members."
The article, "Group-Level Selection Increases Cooperation in the Public Goods Game," provides insight into the origins of group conflict and "supports the notion that competition between groups is part of what has cultivated human cooperation," the authors said.
"History seems to support the idea that a group working together can overcome another group and drive them to extinction," said Wilson, the Herbert S. Autrey Professor of Political Science, professor of statistics and of psychology at Rice. "But it had not been clear whether this was due to groups cooperating when in competition or to pressure of extinction through selection."
The researchers conducted a controlled laboratory experiment to determine whether competition or extinction drives increased cooperation within groups. The experiment was based on the public goods game in which participants in groups are each given a set amount of money. Each group member secretly chooses how much to put into the group account and how much to retain for their own account. The amount in the group account is multiplied by a set factor, and the payoff is equally divided among the members of the group; participants also keep the money they did not contribute to the group account.
In the researchers' experiment, 168 undergraduate students were randomly assigned to groups of four. No participant knew who their fellow group members were, and all interactions were conducted anonymously over a computer network.
The game consisted of two blocks of 10 periods. Each period every subject was given 50 monetary units and decided how much to keep in their private account and how much to put in the group account. The private account paid one to one. The contributions to the group account were doubled by the experimenters, and the total of the group account was divided equally among each member of the group.
"This basic experimental design has been used hundreds of times, and free riding is common," he said. "We wanted to know whether competition or extinction works to eliminate free riding in the way that Darwin suggests."
The researchers used four treatments in their experiment:
The first treatment replicated the standard public goods game. At the end of each period, subjects found out how much was contributed by others in their group to the group account. They were told nothing about the contributions of participants in the other groups.
Group competition was introduced in the second treatment. Subjects saw the same information as in the first treatment; however, they were told that at the end of the first 10 periods their group would be ranked in terms of total earnings against the other groups in the experiment.
In the third treatment, extinction was introduced. Subjects were told that at the end of 10 periods their earnings would be compared with all other subjects' earnings. One-third of the lowest earners would be removed from the experiment and not allowed to participate in the second block of 10 periods.
In the fourth treatment, extinction was applied to groups rather than individuals. Subjects were told that at the end of the first 10 periods their group's earnings would be compared with the other groups' earnings. Groups that fell in the bottom one-third of earners would be removed from the experiment and would not participate in the second block of 10 periods.
The researchers found that in treatments one through three, average contributions declined steadily over the first 10 periods. "Over time, people contribute less to the public good and favor their private investments," Wilson said.
"But when we introduce group extinction, we see a remarkably different result," he said. "At the outset, individuals contribute almost everything to the group account. The pressure of group extinction results in individuals cooperating within the group."
Researchers found that group extinction, the fourth treatment, led to greater contributions to the group account (92 percent of the endowment, on average) than any other treatment (35 percent in first treatment, 36 percent in third treatment, or individual extinction, and 42 percent in the second treatment, group comparison).
The authors noted that "group extinction leads to enhanced cooperation as long as the selection mechanism is present. Once it is removed, contributions remain higher for a time, but fall quickly toward ... zero contributions. The culture of cooperation engendered by the group extinction mechanism has only a brief longer-term carryover after the mechanism is removed."

EEG recordings prove learning foreign languages can sharpen our minds

Learning a foreign language helps the brain.

Credit: © eikotsuttiy / Fotolia

Scientists from the Higher School of Economics (HSE) together with colleagues from the University of Helsinki have discovered that learning foreign languages enhances the our brain's elasticity and its ability to code information. The more foreign languages we learn, the more effectively our brain reacts and processes the data accumulated in the course of learning. An article of Yury Shtyrov, Leading Research Fellow of the HSE Centre for Cognition & Decision Making, Lilli Kimppa and Teija Kujala (University of Helsinki) summarizing the new findings has been recently published in Scientific Reports.

According to the study, the neurophysiological mechanics of language and speech acquisition are underexplored when compared to the brain's other functions. The reason for such scarce attention is the inability to study verbal function on test animals.
Researchers carried out experiments where the brain's electrical activity was measured with EEG (electroencephalography). Twenty-two students in total (10 male and 12 female) participated in the investigation, with the average age being 24. The subjects had electrodes placed on their heads and then listened to recordings of different words in their native language, as well in foreign languages, both known and completely unknown by the subjects. When the known or unknown words popped up, changes in the brain's activity were tracked. Researchers especially focused on the speed at which the brain readjusted its activity to treat unknown words. Afterwards, the accrued neurophysiological data was compared to the subjects' linguistic background: how many languages they knew, at which age they started to learn it, and so on. Apparently, the ability of the brain to quickly process information depends on one's "linguistic anamneses."
The experiment has shown that the brain's electrical activity of those participants who had already known some foreign languages, was higher. The author of the study, Yuriy Shtyrov commented that the more languages someone mastered, the faster the neuron network coding the information on the new words was formed. Consequently, this new data stimulates the brain's physiology: loading the mind with more knowledge boosts its elasticity.
Scientists believe that understanding how the brain functions in acquiring language is of crucial importance in diagnosing speech impediments after accidents, strokes, and other related conditions, and finding ways to treat them. Moreover, when we achieve better insight into the principles of creating and strengthening neuron networks, we will be able to harness these mechanisms, speed them up and improve the learning process.

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The above post is reprinted from materials provided by National Research University Higher School of Economics. Note: Content may be edited for style and length.

Engineers develop a plastic clothing material that cools the skin

Stanford researchers began with a sheet of polyethylene and modified it with a series of chemical treatments, resulting in a cooling fabric.

Credit: L.A. Cicero

Stanford School of Engineering,

Stanford engineers have developed a low-cost, plastic-based textile that, if woven into clothing, could cool your body far more efficiently than is possible with the natural or synthetic fabrics in clothes we wear today.

Describing their work in Science, the researchers suggest that this new family of fabrics could become the basis for garments that keep people cool in hot climates without air conditioning.
"If you can cool the person rather than the building where they work or live, that will save energy," said Yi Cui, an associate professor of materials science and engineering and of photon science at Stanford.
This new material works by allowing the body to discharge heat in two ways that would make the wearer feel nearly 4 degrees Fahrenheit cooler than if they wore cotton clothing.
The material cools by letting perspiration evaporate through the material, something ordinary fabrics already do. But the Stanford material provides a second, revolutionary cooling mechanism: allowing heat that the body emits as infrared radiation to pass through the plastic textile.
All objects, including our bodies, throw off heat in the form of infrared radiation, an invisible and benign wavelength of light. Blankets warm us by trapping infrared heat emissions close to the body. This thermal radiation escaping from our bodies is what makes us visible in the dark through night-vision goggles.
"Forty to 60 percent of our body heat is dissipated as infrared radiation when we are sitting in an office," said Shanhui Fan, a professor of electrical engineering who specializes in photonics, which is the study of visible and invisible light. "But until now there has been little or no research on designing the thermal radiation characteristics of textiles."
Super-powered kitchen wrap
To develop their cooling textile, the Stanford researchers blended nanotechnology, photonics and chemistry to give polyethylene -- the clear, clingy plastic we use as kitchen wrap -- a number of characteristics desirable in clothing material: It allows thermal radiation, air and water vapor to pass right through, and it is opaque to visible light.
The easiest attribute was allowing infrared radiation to pass through the material, because this is a characteristic of ordinary polyethylene food wrap. Of course, kitchen plastic is impervious to water and is see-through as well, rendering it useless as clothing.
The Stanford researchers tackled these deficiencies one at a time.
First, they found a variant of polyethylene commonly used in battery making that has a specific nanostructure that is opaque to visible light yet is transparent to infrared radiation, which could let body heat escape. This provided a base material that was opaque to visible light for the sake of modesty but thermally transparent for purposes of energy efficiency.
They then modified the industrial polyethylene by treating it with benign chemicals to enable water vapor molecules to evaporate through nanopores in the plastic, said postdoctoral scholar and team member Po-Chun Hsu, allowing the plastic to breathe like a natural fiber.
Making clothes
That success gave the researchers a single-sheet material that met their three basic criteria for a cooling fabric. To make this thin material more fabric-like, they created a three-ply version: two sheets of treated polyethylene separated by a cotton mesh for strength and thickness.
To test the cooling potential of their three-ply construct versus a cotton fabric of comparable thickness, they placed a small swatch of each material on a surface that was as warm as bare skin and measured how much heat each material trapped.
"Wearing anything traps some heat and makes the skin warmer," Fan said. "If dissipating thermal radiation were our only concern, then it would be best to wear nothing."
The comparison showed that the cotton fabric made the skin surface 3.6 F warmer than their cooling textile. The researchers said this difference means that a person dressed in their new material might feel less inclined to turn on a fan or air conditioner.
The researchers are continuing their work on several fronts, including adding more colors, textures and cloth-like characteristics to their material. Adapting a material already mass produced for the battery industry could make it easier to create products.
"If you want to make a textile, you have to be able to make huge volumes inexpensively," Cui said.
Fan believes that this research opens up new avenues of inquiry to cool or heat things, passively, without the use of outside energy, by tuning materials to dissipate or trap infrared radiation.
"In hindsight, some of what we've done looks very simple, but it's because few have really been looking at engineering the radiation characteristics of textiles," he said.

First stars formed even later than previously thought

Cosmic reionisation.

Credit: ESA – C. Carreau

European Space Agency,

ESA's Planck satellite has revealed that the first stars in the Universe started forming later than previous observations of the Cosmic Microwave Background indicated. This new analysis also shows that these stars were the only sources needed to account for reionising atoms in the cosmos, having completed half of this process when the Universe had reached an age of 700 million years.

With the multitude of stars and galaxies that populate the present Universe, it's hard to imagine how different our 13.8 billion year cosmos was when it was only a few seconds old. At that early phase, it was a hot, dense primordial soup of particles, mostly electrons, protons, neutrinos, and photons -- the particles of light.
In such a dense environment the Universe appeared like an 'opaque' fog, as light particles could not travel any significant distance before colliding with electrons.
As the cosmos expanded, the Universe grew cooler and more rarefied and, after about 380,000 years, finally became 'transparent'. By then, particle collisions were extremely sporadic and photons could travel freely across the cosmos.
Today, telescopes like Planck can observe this fossil light across the entire sky as the Cosmic Microwave Background, or CMB. Its distribution on the sky reveals tiny fluctuations that contain a wealth of information about the history, composition and geometry of the Universe.
The release of the CMB happened at the time when electrons and protons joined to form hydrogen atoms. This is the first moment in the history of the cosmos when matter was in an electrically neutral state.
After that, a few hundred million years passed before these atoms could assemble and eventually give rise to the Universe's first generation of stars.
As these first stars came to life, they filled their surroundings with light, which subsequently split neutral atoms apart, turning them back into their constituent particles: electrons and protons. Scientists refer to this as the 'epoch of reionisation'. It did not take long for most material in the Universe to become completely ionised, and -- except in a very few, isolated places -- it has been like that ever since.
Observations of very distant galaxies hosting supermassive black holes indicate that the Universe had been completely reionised by the time it was about 900 million years old. The starting point of this process, however, is much harder to determine and has been a hotly debated topic in recent years.
"The CMB can tell us when the epoch of reionisation started and, in turn, when the first stars formed in the Universe," explains Jan Tauber, Planck project scientist at ESA.
To make this measurement, scientists exploit the fact that a fraction of the CMB is polarised: part of the light vibrates in a preferred direction. This results from CMB photons bouncing off electrons -- something that happened very frequently in the primordial soup, before the CMB was released, and then again later, after reionisation, when light from the first stars brought free electrons back onto the cosmic stage.
"It is in the tiny fluctuations of the CMB polarisation that we can see the influence of the reionisation process and deduce when it began," adds Tauber.
A first estimate of the epoch of reionisation came in 2003 from NASA's Wilkinson Microwave Anisotropy Probe (WMAP), suggesting that this process might have started early in cosmic history, when the Universe was only a couple of hundred million years old. This result was problematic, because there is no evidence that any stars had formed by then, which would mean postulating the existence of other, exotic sources that could have caused the reionisation at that time.
This first estimate was soon to be corrected, as subsequent data from WMAP pushed the starting time to later epochs, indicating that the Universe had not been significantly reionised until at least some 450 million years into its history.
This eased, but did not completely solve the puzzle: although the earliest of the first stars have been observed to be present already when the Universe was 300 to 400 million years old, it remained unclear whether these stars were the main culprits for reionising fully the cosmos or whether additional, more exotic sources must have played a role too.
In 2015, the Planck Collaboration provided new data to tackle the problem, moving the reionisation epoch even later in cosmic history and revealing that this process was about half-way through when the Universe was around 550 million years old. The result was based on Planck's first all-sky maps of the CMB polarisation, obtained with its Low-Frequency Instrument (LFI).
Now, a new analysis of data from Planck's other detector, the High-Frequency Instrument (HFI), which is more sensitive to this phenomenon than any other so far, shows that reionisation started even later -- much later than any previous data have suggested.
"The highly sensitive measurements from HFI have clearly demonstrated that reionisation was a very quick process, starting fairly late in cosmic history and having half-reionised the Universe by the time it was about 700 million years old," says Jean-Loup Puget from Institut d'Astrophysique Spatiale in Orsay, France, principal investigator of Planck's HFI.
"These results are now helping us to model the beginning of the reionisation phase."
"We have also confirmed that no other agents are needed, besides the first stars, to reionise the Universe," adds Matthieu Tristram, a Planck Collaboration scientist at Laboratoire de l'Accélérateur Linéaire in Orsay, France.
The new study locates the formation of the first stars much later than previously thought on the cosmic timeline, suggesting that the first generation of galaxies are well within the observational reach of future astronomical facilities, and possibly even some current ones.
In fact, it is likely that some of the very first galaxies have already been detected with long exposures, such as the Hubble Ultra Deep Field observed with the NASA/ESA Hubble Space Telescope, and it will be easier than expected to catch many more with future observatories such as the NASA/ESA/CSA James Webb Space Telescope.

How to Set an Expiry Date for Google Drive Share Links

Set an Expiry Date for Google Drive Share Links to make them unusable after fixed interval of time to avoid misuse of the files or other security reasons can be there, so it is better to set the expiry dates to the links you share.

Google Drive is the online store place for your data and files etc. and by using it you can easily store, manage all your files and other data. Using the
G
Google Drive

, you can even share your files online to anyone hence making it easy for transferring data. To send or to share up the files with anyone, you will have to upload the file to the

Google Drive

and then get up the sharing link for that file and then send that link to someone for multiple times. Once you have shared that link with anyone, he/she will be able to access your file or data through that share link until that file/data remain in your

Google Drive

account. In case you don’t want that your data should be accessible forever until it has been removed then there is one way through which you can set the expiry date for the Google

share links

by which the links cannot be used anymore to access your data after the elapsed time that you have

set

. So have a look on complete guide discussed below to proceed.

The method is quite straightforward and easy, and you just need to follow the simple steps below to proceed.

1. First of all, you will have to open up the “Script Page” on your web browser and then make it work with your Google Drive account. This will be very simple to do as you will be asked for the access to your Google Drive account once you load up the script page on your browser.
2. Just read up the whole permissions that are required by clicking on the ‘Review Permissions‘ button on the script page. Remember to read up the full leaves as these are paramount and greatly related to your account.

3. After accepting the permissions, you can then use the script page to contact with your Google Drive account.
4. Just select up the file from your Google Drive that you want to share with the link set to Expire after some time. To choose the file click on the ‘Open Drive’ button on the script page and then log in to your Google Drive account and then from there get up the file you want to share.
4. Now inside the script page only, you will have to fill the email addresses to whom you want to send the selected file and then in the next step on the same page only you can set up the expiry time too.
5. Once you have set up the expiry time for the share links that the script page has automatically generated for the selected file, your file will be then shared and with the Expiry time feature.
Note: You can also cancel the shared links or you can delete the shared link before the expiry time also by clicking on the ‘Cancel’ option placed aside the shared files details.
So that’s the simplest method by which you can quickly set up the Expiry date for the Google Drive share links and hence you can make your transfers much safer, and also your Google Drive Account as through that links there can be the chances that your Google Drive account could be hacked. To make sure that your have secure data transfers through your Google Drive you should always set up the Expiry Date for your Share links.

Hubble captures vivid auroras in Jupiter’s atmosphere

This image combines an image taken with Hubble Space Telescope in the optical (taken in spring 2014) and observat ions of its auroras in the ultraviolet, taken in 2016.

Credit: NASA, ESA

Astronomers are using the NASA/ESA Hubble Space Telescope to study auroras -- stunning light shows in a planet's atmosphere -- on the poles of the largest planet in the Solar System, Jupiter. This observation programme is supported by measurements made by NASA's Juno spacecraft, currently on its way to Jupiter.

Jupiter, the largest planet in the Solar System, is best known for its colourful storms, the most famous being the Great Red Spot. Now astronomers have focused on another beautiful feature of the planet, using the ultraviolet capabilities of the NASA/ESA Hubble Space Telescope.
The extraordinary vivid glows shown in the new observations are known as auroras [1]. They are created when high energy particles enter a planet's atmosphere near its magnetic poles and collide with atoms of gas. As well as producing beautiful images, this programme aims to determine how various components of Jupiter's auroras respond to different conditions in the solar wind, a stream of charged particles ejected from the Sun.
This observation programme is perfectly timed as NASA's Juno spacecraft is currently in the solar wind near Jupiter and will enter the orbit of the planet in early July 2016. While Hubble is observing and measuring the auroras on Jupiter, Juno is measuring the properties of the solar wind itself; a perfect collaboration between a telescope and a space probe [2].
"These auroras are very dramatic and among the most active I have ever seen," says Jonathan Nichols from the University of Leicester, UK, and principal investigator of the study. "It almost seems as if Jupiter is throwing a firework party for the imminent arrival of Juno."
To highlight changes in the auroras Hubble is observing Jupiter daily for around one month. Using this series of images it is possible for scientists to create videos that demonstrate the movement of the vivid auroras, which cover areas bigger than the Earth.
Not only are the auroras huge, they are also hundreds of times more energetic than auroras on Earth. And, unlike those on Earth, they never cease. Whilst on Earth the most intense auroras are caused by solar storms -- when charged particles rain down on the upper atmosphere, excite gases, and cause them to glow red, green and purple -- Jupiter has an additional source for its auroras.
The strong magnetic field of the gas giant grabs charged particles from its surroundings. This includes not only the charged particles within the solar wind but also the particles thrown into space by its orbiting moon Io, known for its numerous and large volcanos.
The new observations and measurements made with Hubble and Juno will help to better understand how the Sun and other sources influence auroras. While the observations with Hubble are still ongoing and the analysis of the data will take several more months, the first images and videos are already available and show the auroras on Jupiter's north pole in their full beauty.
Notes
[1] Jupiter's auroras were first discovered by the Voyager 1 spacecraft in 1979. A thin ring of light on Jupiter's nightside looked like a stretched-out version of our own auroras on Earth. Only later on was it discovered that the auroras were best visible in the ultraviolet.
[2] This is not the first time astronomers have used Hubble to observe the auroras on Jupiter, nor is it the first time that Hubble has cooperated with space probes to do so. In 2000 the NASA/ESA Cassini spacecraft made its closest approach to Jupiter and scientists used this opportunity to gather data and images about the auroras simultaneously from Cassini and Hubble (heic0009). In 2007 Hubble obtained images in support of its sister NASA Mission New Horizons which used Jupiter's gravity for a manoeuvre on its way to Pluto (opo0714a).

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The above post is reprinted from materials provided by University of Leicester. Note: Content may be edited for style and length

Ceres' geological activity, ice revealed in new research

Ceres' lonely mountain, Ahuna Mons, is seen in this simulated perspective view. The elevation has been exaggerated by a factor of two.

Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI

A lonely 3-mile-high (5-kilometer-high) mountain on Ceres is likely volcanic in origin, and the dwarf planet may have a weak, temporary atmosphere. These are just two of many new insights about Ceres from NASA's Dawn mission published this week in six papers in the journal Science.

"Dawn has revealed that Ceres is a diverse world that clearly had geological activity in its recent past," said Chris Russell, principal investigator of the Dawn mission, based at the University of California, Los Angeles.
A Temporary Atmosphere
A surprising finding emerged in the paper led by Russell: Dawn may have detected a weak, temporary atmosphere. Dawn's gamma ray and neutron (GRaND) detector observed evidence that Ceres had accelerated electrons from the solar wind to very high energies over a period of about six days. In theory, the interaction between the solar wind's energetic particles and atmospheric molecules could explain the GRaND observations.
A temporary atmosphere would be consistent with the water vapor the Herschel Space Observatory detected at Ceres in 2012-2013. The electrons that GRaND detected could have been produced by the solar wind hitting the water molecules that Herschel observed, but scientists are also looking into alternative explanations.
"We're very excited to follow up on this and the other discoveries about this fascinating world," Russell said.
Ahuna Mons as a Cryovolcano
Ahuna Mons is a volcanic dome unlike any seen elsewhere in the solar system, according to a new analysis led by Ottaviano Ruesch of NASA's Goddard Space Flight Center, Greenbelt, Maryland, and the Universities Space Research Association. Ruesch and colleagues studied formation models of volcanic domes, 3-D terrain maps and images from Dawn, as well as analogous geological features elsewhere in our solar system. This led to the conclusion that the lonely mountain is likely volcanic in nature. Specifically, it would be a cryovolcano -- a volcano that erupts a liquid made of volatiles such as water, instead of silicates. "This is the only known example of a cryovolcano that potentially formed from a salty mud mix, and that formed in the geologically recent past," Ruesch said.
For more details on this study, see:
http://www.nasa.gov/feature/goddard/2016/ceres-cryo-volcano
Ceres: Between a Rocky and Icy Place
While Ahuna Mons may have erupted liquid water in the past, Dawn has detected water in the present, as described in a study led by Jean-Philippe Combe of the Bear Fight Institute, Winthrop, Washington. Combe and colleagues used Dawn's visible and infrared mapping spectrometer (VIR) to detect probable water ice at Oxo Crater, a small, bright, sloped depression at mid-latitudes on Ceres.
Exposed water-ice is rare on Ceres, but the low density of Ceres, the impact-generated flows and the very existence of Ahuna Mons suggest that Ceres' crust does contain a significant component of water-ice. This is consistent with a study of Ceres' diverse geological features led by Harald Hiesinger of the Westfälische Wilhelms-Universität, Münster, Germany. The diversity of geological features on Ceres is further explored in a study led by Debra Buczkowski of the Johns Hopkins Applied Physics Laboratory, Laurel, Maryland.
Impact craters are clearly the most abundant geological feature on Ceres, and their different shapes help tell the intricate story of Ceres' past. Craters that are roughly polygonal -- that is, shapes bounded by straight lines -- hint that Ceres' crust is heavily fractured. In addition, several Cerean craters have patterns of visible fractures on their floors.
Some, like tiny Oxo, have terraces, while others, such as the large Urvara Crater (106 miles, 170 kilometers wide), have central peaks. There are craters with flow-like features, and craters that imprint on other craters, as well as chains of small craters. Bright areas are peppered across Ceres, with the most reflective ones in Occator Crater. Some crater shapes could indicate water-ice in the subsurface.
The dwarf planet's various crater forms are consistent with an outer shell for Ceres that is not purely ice or rock, but rather a mixture of both -- a conclusion reflected in other analyses. Scientists also calculated the ratio of various craters' depths to diameters, and found that some amount of crater relaxation must have occurred. Additionally, there are more craters in the northern hemisphere of Ceres than the south, where the large Urvara and Yalode craters are the dominant features.
"The uneven distribution of craters indicates that the crust is not uniform, and that Ceres has gone through a complex geological evolution," Hiesinger said.
Distribution of Surface Materials
What are the rocky materials in Ceres' crust? A study led by Eleonora Ammannito of the University of California, Los Angeles, finds that clay-forming minerals called phyllosilicates are all over Ceres. These phyllosilicates are rich in magnesium and also have some ammonium embedded in their crystalline structure. Their distribution throughout the dwarf planet's crust indicates Ceres' surface material has been altered by a global process involving water.
Although Ceres' phyllosilicates are uniform in their composition, there are marked differences in how abundant these materials are on the surface. For example, phyllosilicates are especially prevalent in the region around the smooth, "pancake"-like crater Kerwan (174 miles, 280 kilometers in diameter), and less so at Yalode Crater (162 miles, 260 kilometers in diameter), which has areas of both smooth and rugged terrain around it. Since Kerwan and Yalode are similar in size, this may mean that the composition of the material into which they impacted may be different. Craters Dantu and Haulani both formed recently in geologic time, but also seem to differ in composition.
"In comparing craters such as Dantu and Haulani, we find that their different material mixtures could extend beneath the surface for miles, or even tens of miles in the case of the larger Dantu," Ammannito said.
Looking Higher
Now in its extended mission, the Dawn spacecraft has delivered a wealth of images and other data from its current perch at 240 miles (385 kilometers) above Ceres' surface, which is closer to the dwarf planet than the International Space Station is to Earth. The spacecraft will be increasing its altitude at Ceres on Sept. 2, as scientists consider questions that can be examined from higher up.
Dawn's mission is managed by JPL for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team. For a complete list of mission participants, visit:


http://dawn.jpl.nasa.gov/mission
More information about Dawn is available at the following sites:
http://dawn.jpl.nasa.gov
http://www.nasa.gov/dawn