Oceans arrived early to Earth via Meteorites

Earth is known as the Blue Planet because of its oceans, which cover more than 70 percent of the planet’s surface and are home to the world’s greatest diversity of life. While water is essential for life on the planet, the answers to two key questions have eluded us: where did Earth’s water come from and when?

In this illustration of the early solar system, the dashed white line represents the snow line -- the transition from the hotter inner solar system, where water ice is not stable (brown) to the outer Solar system, where water ice is stable (blue). Two possible ways that the inner solar system received water are: water molecules sticking to dust grains inside the "snow line" (as shown in the inset) and carbonaceous chondrite material flung into the inner solar system by the effect of gravity from protoJupiter. With either scenario, water must accrete to the inner planets within the first ca. 10 million years of solar system formation.
In this illustration of the early solar system, the dashed white line represents the snow line — the transition from the hotter inner solar system, where water ice is not stable (brown) to the outer Solar system, where water ice is stable (blue). Two possible ways that the inner solar system received water are: water molecules sticking to dust grains inside the “snow line” (as shown in the inset) and carbonaceous chondrite material flung into the inner solar system by the effect of gravity from protoJupiter. With either scenario, water must accrete to the inner planets within the first ca. 10 million years of solar system formation.

Credit: Illustration by Jack Cook, Woods Hole Oceanographic Institution

While some hypothesize that water came late to Earth, well after the planet had formed, findings from a new study led by scientists at the Woods Hole Oceanographic Institution (WHOI) significantly move back the clock for the first evidence of water on Earth and in the inner solar system.

“The answer to one of the basic questions is that our oceans were always here. We didn’t get them from a late process, as was previously thought,” said Adam Sarafian, the lead author of the paper published Oct. 31, 2014, in the journal Science and a MIT/WHOI Joint Program student in the Geology and Geophysics Department.

One school of thought was that planets originally formed dry, due to the high-energy, high-impact process of planet formation, and that the water came later from sources such as comets or “wet” asteroids, which are largely composed of ices and gases.

“With giant asteroids and meteors colliding, there’s a lot of destruction,” said Horst Marschall, a geologist at WHOI and coauthor of the paper. “Some people have argued that any water molecules that were present as the planets were forming would have evaporated or been blown off into space, and that surface water as it exists on our planet today, must have come much, much later — hundreds of millions of years later.”

The study’s authors turned to another potential source of Earth’s water — carbonaceous chondrites. The most primitive known meteorites, carbonaceous chondrites, were formed in the same swirl of dust, grit, ice and gasses that gave rise to the sun some 4.6 billion years ago, well before the planets were formed.

“These primitive meteorites resemble the bulk solar system composition,” said WHOI geologist and coauthor Sune Nielsen. “They have quite a lot of water in them, and have been thought of before as candidates for the origin of Earth’s water.”

In order to determine the source of water in planetary bodies, scientists measure the ratio between the two stable isotopes of hydrogen: deuterium and hydrogen. Different regions of the solar system are characterized by highly variable ratios of these isotopes. The study’s authors knew the ratio for carbonaceous chondrites and reasoned that if they could compare that to an object that was known to crystallize while Earth was actively accreting then they could gauge when water appeared on Earth.

To test this hypothesis, the research team, which also includes Francis McCubbin from the Institute of Meteoritics at the University of New Mexico and Brian Monteleone of WHOI, utilized meteorite samples provided by NASA from the asteroid 4-Vesta. The asteroid 4-Vesta, which formed in the same region of the solar system as Earth, has a surface of basaltic rock — frozen lava. These basaltic meteorites from 4-Vesta are known as eucrites and carry a unique signature of one of the oldest hydrogen reservoirs in the solar system. Their age — approximately 14 million years after the solar system formed — makes them ideal for determining the source of water in the inner solar system at a time when Earth was in its main building phase. The researchers analyzed five different samples at the Northeast National Ion Microprobe Facility — a state-of-the-art national facility housed at WHOI that utilizes secondary ion mass spectrometers. This is the first time hydrogen isotopes have been measured in eucrite meteorites.

The measurements show that 4-Vesta contains the same hydrogen isotopic composition as carbonaceous chondrites, which is also that of Earth. That, combined with nitrogen isotope data, points to carbonaceous chondrites as the most likely common source of water.

“The study shows that Earth’s water most likely accreted at the same time as the rock. The planet formed as a wet planet with water on the surface,” Marschall said.

While the findings don’t preclude a late addition of water on Earth, it shows that it wasn’t necessary since the right amount and composition of water was present at a very early stage.

“An implication of that is that life on our planet could have started to begin very early,” added Nielsen. “Knowing that water came early to the inner solar system also means that the other inner planets could have been wet early and evolved life before they became the harsh environments they are today.”

courtesy: Woods Hole Oceanographic Institution

Understanding the Past and Predicting the Future by Looking Across Space and Time

Studying complex systems like ecosystems can get messy, especially when trying to predict how they interact with other big unknowns like climate change.In a new paper published this week (May 20) in the Proceedings of the National Academy of Sciences, researchers from the University of Wisconsin-Madison and elsewhere validate a fundamental assumption at the very heart of a popular way to predict relationships between complex variables.

studying ecosystem


Studying complex systems like ecosystems can get messy, especially when trying to predict how they interact with other big unknowns like climate change. (Credit: © arquiplay77 / Fotolia)

To model how climate changes may impact biodiversity, researchers like Jessica Blois and John W. (Jack) Williams routinely use an approach called “space-for-time substitution.” The idea behind this method is to use the information in current geographic distributions of species to build a model that can predict climate-driven ecological changes in the past or future. But does it really work?

“It’s a necessary assumption, but it’s generally untested,” says lead study author Blois, a former postdoctoral fellow with Williams at UW-Madison. She is now an assistant professor at the University of California, Merced. “Yet we’re using this every day when we make predictions about biodiversity going into the future with climate change.”

Their results should give other ecologists — and potentially others such as economists who use similar models — more confidence in their methods.

“At these spatial and temporal scales, the space-for-time assumption does work well,” says Williams, professor of geography and director of the Center for Climatic Research at the UW-Madison Nelson Institute for Environmental Studies. “Our fossil data did support the idea that you can use spatial relationships as a source of information for making these predictions for the future.”

Their research focus is paleoecology, the study of ancient ecosystems. By looking at fossilized pollen trapped in cores of sediment from the bottoms of lakes, the scientists reconstructed information about the plant communities present at locations across eastern North America during the past 21,000 years.

If climate has influenced communities the same way across space and through time, Blois explains, then a model based on the spatial data should make the same predictions as a model based on their temporal data. And in fact, they did.

The space-for-time model explained about 72 percent of the variation seen in their time data, and the remainder is likely due to other biological and environmental factors that the simplified model does not include, Blois says.

Though the testing does not capture all the ways space-for-time substitutions are used in other predictive fields, she says that the results are very encouraging for questions spanning large geographic and time scales — scales at which collecting good temporal data can be very challenging.

“We found that at these broad time scales we’re looking at, that space does substitute for time relatively well,” Blois says. “It makes me more confident in my analyses going forward.”

courtesy: sciencedaily

Detection of the Cosmic Gamma Ray Horizon

How much light has been emitted by all galaxies since the cosmos began? After all, almost every photon (particle of light) from ultraviolet to far infrared wavelengths ever radiated by all galaxies that ever existed throughout cosmic history is still speeding through the Universe today. If we could carefully measure the number and energy (wavelength) of all those photons — not only at the present time, but also back in time — we might learn important secrets about the nature and evolution of the Universe, including how similar or different ancient galaxies were compared to the galaxies we see today.


detection of cosmic rays

The attached figure illustrates how energetic gamma rays (dashed lines) from a distant blazar strike photons of extragalactic background light (wavy lines) and produce pairs of electrons and positrons. The energetic gamma rays that are not attenuated by this process strike the upper atmosphere, producing a cascade of charged particles which make a cone of erenkov light that is detected by the array of imaging atmospheric erenkov telescopes on the ground. (Credit: Nina McCurdy and Joel R. Primack/UC-HiPACC; Blazar: Frame from a conceptual animation of 3C 120 created by Wolfgang Steffen/UNAM)

That bath of ancient and young photons suffusing the Universe today is called the extragalactic background light (EBL). An accurate measurement of the EBL is as fundamental to cosmology as measuring the heat radiation left over from the Big Bang (the cosmic microwave background) at radio wavelengths. A new paper, called “Detection of the Cosmic γ-Ray Horizon from Multiwavelength Observations of Blazars,” by Alberto Dominguez and six coauthors, just published today by theAstrophysical Journal — based on observations spanning wavelengths from radio waves to very energetic gamma rays, obtained from several NASA spacecraft and several ground-based telescopes — describes the best measurement yet of the evolution of the EBL over the past 5 billion years.

Directly measuring the EBL by collecting its photons with a telescope, however, poses towering technical challenges — harder than trying to see the dim band of the Milky Way spanning the heavens at night from midtown Manhattan. Earth is inside a very bright galaxy with billions of stars and glowing gas. Indeed, Earth is inside a very bright solar system: sunlight scattered by all the dust in the plane of Earth’s orbit creates the zodiacal light radiating across the optical spectrum down to long-wavelength infrared. Therefore ground-based and space-based telescopes have not succeeded in reliably measuring the EBL directly.

So, astrophysicists developed an ingenious work-around method: measuring the EBL indirectly through measuring the attenuation of — that is, the absorption of — very high energy gamma rays from distant blazars. Blazars are supermassive black holes in the centers of galaxies with brilliant jets directly pointed at us like a flashlight beam. Not all the high-energy gamma rays emitted by a blazar, however, make it all the way across billions of light-years to Earth; some strike a hapless EBL photon along the way. When a high-energy gamma ray photon from a blazar hits a much lower energy EBL photon, both are annihilated and produce two different particles: an electron and its antiparticle, a positron, which fly off into space and are never heard from again. Different energies of the highest-energy gamma rays are waylaid by different energies of EBL photons. Thus, measuring how much gamma rays of different energies are attenuated or weakened from blazars at different distances from Earth indirectly gives a measurement of how many EBL photons of different wavelengths exist along the line of sight from blazar to Earth over those different distances.

Observations of blazars by NASA’s Fermi Gamma Ray Telescope spacecraft for the first time detected that gamma rays from distant blazars are indeed attenuated more than gamma rays from nearby blazars, a result announced on November 30, 2012, in a paper published in Science, as theoretically predicted.

Now, the big news — announced in today’s Astrophysical Journal paper — is that the evolution of the EBL over the past 5 billion years has been measured for the first time. That’s because looking farther out into the Universe corresponds to looking back in time. Thus, the gamma ray attenuation spectrum from farther distant blazars reveals how the EBL looked at earlier eras.

This was a multistep process. First, the coauthors compared the Fermi findings to intensity of X-rays from the same blazars measured by X-ray satellites Chandra, Swift, Rossi X-ray Timing Explorer, and XMM/Newton and lower-energy radiation measured by other spacecraft and ground-based observatories. From these measurements, Dominguez et al. were able to calculate the blazars’ original emitted, unattenuated gamma-ray brightnesses at different energies.

The coauthors then compared those calculations of unattenuated gamma-ray flux at different energies with direct measurements from special ground-based telescopes of the actual gamma-ray flux received at Earth from those same blazars. When a high-energy gamma ray from a blazar strikes air molecules in the upper regions of Earth’s atmosphere, it produces a cascade of charged subatomic particles. This cascade of particles travels faster than the speed of light in air (which is slower than the speed of light in a vacuum). This causes a visual analogue to a “sonic boom”: bursts of a special light called Čerenkov radiation. This Čerenkov radiation was detected by imaging atmospheric Čerenkov telescopes (IACTs), such as HESS (High Energy Stereoscopic System) in Namibia, MAGIC (Major Atmospheric Gamma Imaging Čerenkov) in the Canary Islands, and VERITAS (Very Energetic Radiation Imaging Telescope Array Systems) in Arizona.

Comparing the calculations of the unattenuated gamma rays to actual measurements of the attenuation of gamma rays and X-rays from blazars at different distances allowed Dominquez et al. to quantify the evolution of the EBL — that is, to measure how the EBL changed over time as the Universe aged — out to about 5 billion years ago (corresponding to a redshift of about z = 0.5). “Five billion years ago is the maximum distance we are able to probe with our current technology,” Domínguez said. “Sure, there are blazars farther away, but we are not able to detect them because the high-energy gamma rays they are emitting are too attenuated by EBL when they get to us — so weakened that our instruments are not sensitive enough to detect them.” This measurement is the first statistically significant detection of the so-called “Cosmic Gamma Ray Horizon” as a function of gamma-ray energy. The Cosmic Gamma Ray Horizon is defined as the distance at which roughly one-third (or, more precisely, 1/e — that is, 1/2.718 — where e is the base of the natural logarithms) of the gamma rays of a particular energy have been attenuated.

This latest result confirms that the kinds of galaxies observed today are responsible for most of the EBL over all time. Moreover, it sets limits on possible contributions from many galaxies too faint to have been included in the galaxy surveys, or on possible contributions from hypothetical additional sources (such as the decay of hypothetical unknown elementary particles).

courtesy: sciencedaily

Scientists found Billion-Year-Old Water

Scientists working 2.4 kilometers below Earth’s surface in a Canadian mine have tapped a source of water that has remained isolated for at least a billion years. The researchers say they do not yet know whether anything has been living in it all this time, but the water contains high levels of methane and hydrogen — the right stuff to support life.

The ancient water contains chemicals that could support life without sunlight. ( Pic courtesy: National Geographic )


Micrometer-scale pockets in minerals billions of years old can hold water that was trapped during the minerals’ formation. But no source of free-flowing water passing through interconnected cracks or pores in Earth’s crust has previously been shown to have stayed isolated for more than tens of millions of years.

“We were expecting these fluids to be possibly tens, perhaps even hundreds of millions of years of age,” says Chris Ballentine, a geochemist at the University of Manchester, UK. He and his team carefully captured water flowing through fractures in the 2.7-billion-year-old sulphide deposits in a copper and zinc mine near Timmins, Ontario, ensuring that the water did not come into contact with mine air.

To date the water, the team used three lines of evidence, all based on the relative abundances of various isotopes of noble gases present in the water. The authors determined that the fluid could not have contacted Earth’s atmosphere — and so been at the planet’s surface — for at least 1 billion years, and possibly for as long as 2.64 billion years, not long after the rocks it flows through formed.

Teeming With Life?

Geologists have long known that a lot of water can be present in continental crust, locked away in microscopic voids in minerals, pore spaces between minerals, and veins and fractures in the rock. But what’s been unclear is the age of such water, said geochemist Steven Shirey, a senior scientist at the Carnegie Institution for Science.

“The question is how old is it? Is it water that’s part of current circulation with surface water? Or is it water that retains old chemistry and potential biota?” said Shirey, who was not involved in the study.

The new findings, detailed in this week’s issue of the journal Nature, is evidence that ancient pockets of water can remain isolated in the Earth’s crust for billions of years.

“That’s the really exciting part about this study,” Shirey said.

Sherwood Lollar and her team are testing the mine water to see if they can find evidence of living microbes. If life does exist in the water, she said, it could be similar to microbes previously found in far younger water flowing from a mine located 1.74 miles (2.8 kilometers) beneath South Africa.

Those microbes could survive without light from the sun, subsisting instead on chemicals created through the interactions between water and rock.

Such “buried” microbial communities are rare, and fascinating for scientists because they are often not interconnected.

“Each one of them may have a different age and a different history,” Sherwood Lollar said. “It will be fascinating for us to look at the microbiology in each of them … It’ll tell us something about the evolution of life and the colonization of the subsurface.”

Expanding Horizons

The Timmins Mine water could also help scientists understand how much of the subsurface of the Earth is actually inhabited by life. The answer to that question has implications for life on other planets, such as Mars, scientists say.

“It opens up your horizons for what’s possible,” Shirey said. “If you think that you can have microbial life throughout the entire crust of the Earth, then all of a sudden it becomes very possible that life could live on other planets under the right condition.”

That raises questions about potential life in relatively warm rock located beneath the cold surface of Mars, where liquid water could still exist.

“We’re looking at billion-year-old rock here and we can still find flowing water that’s full of the kind of energy that can support life,” Sherwood Lollar said.

“If we find Martian rocks of the same age and in places of similar geology and mineralogy to our site, then there’s every reason to think that we might be able to find the same thing in the deep subsurface of Mars.”

courtesy: Nature

New Way to Look at Dawn of Life

One of the great mysteries of life is how it began. What physical process transformed a nonliving mix of chemicals into something as complex as a living cell?For more than a century, scientists have struggled to reconstruct the key first steps on the road to life. Until recently, their focus has been trained on how the simple building blocks of life might have been synthesized on the early Earth, or perhaps in space. But because it happened so long ago, all chemical traces have long been obliterated, leaving plenty of scope for speculation and disagreement.

living cell


Assorted diatoms. One of the great mysteries of life is how it began. What physical process transformed a nonliving mix of chemicals into something as complex as a living cell? (Credit: NOAA)

Now, a novel approach to the question of life’s origin, proposed by two Arizona State University scientists, attempts to dramatically redefine the problem. The researchers — Paul Davies, an ASU Regents’ Professor and director of the Beyond Center for Fundamental Concepts in Science, and Sara Walker, a NASA post-doctoral fellow at the Beyond Center — published their theory in the Dec. 12 issue of the Royal Society journal Interface.

In a nutshell, the authors shift attention from the “hardware” — the chemical basis of life — to the “software” — its information content. To use a computer analogy, chemistry explains the material substance of the machine, but it won’t function without a program and data. Davies and Walker suggest that the crucial distinction between non-life and life is the way that living organisms manage the information flowing through the system.

“When we describe biological processes we typically use informational narratives — cells send out signals, developmental programs are run, coded instructions are read, genomic data are transmitted between generations and so forth,” Walker said. “So identifying life’s origin in the way information is processed and managed can open up new avenues for research.”

“We propose that the transition from non-life to life is unique and definable,” added Davies. “We suggest that life may be characterized by its distinctive and active use of information, thus providing a roadmap to identify rigorous criteria for the emergence of life. This is in sharp contrast to a century of thought in which the transition to life has been cast as a problem of chemistry, with the goal of identifying a plausible reaction pathway from chemical mixtures to a living entity.”

Focusing on informational development helps move away from some of the inherent disadvantages of trying to pin down the beginnings of chemical life.

“Chemical based approaches,” Walker said, “have stalled at a very early stage of chemical complexity — very far from anything we would consider ‘alive.’ More seriously they suffer from conceptual shortcomings in that they fail to distinguish between chemistry and biology.”

“To a physicist or chemist life seems like ‘magic matter,'” Davies explained. “It behaves in extraordinary ways that are unmatched in any other complex physical or chemical system. Such lifelike properties include autonomy, adaptability and goal-oriented behavior — the ability to harness chemical reactions to enact a pre-programmed agenda, rather than being a slave to those reactions.”

“We believe the transition in the informational architecture of chemical networks is akin to a phase transition in physics, and we place special emphasis on the top-down information flow in which the system as a whole gains causal purchase over its components,” Davies added. “This approach will reveal how the logical organization of biological replicators differs crucially from trivial replication associated with crystals (non-life). By addressing the causal role of information directly, many of the baffling qualities of life are explained.”

The authors expect that, by re-shaping the conceptual landscape in this fundamental way, not just the origin of life, but other major transitions will be explained, for example, the leap from single cells to multi-cellularity.


courtesy: science daily

Simulations Show Warming Range of 1.4 to 3 Degrees by 2050

A project running almost 10,000 climate simulations on volunteers’ home computers has found that a global warming of 3 degrees Celsius by 2050 is ‘equally plausible’ as a rise of 1.4 degrees.The study, the first to run so many simulations using a complex atmosphere-ocean climate model, addresses some of the uncertainties that previous forecasts, using simpler models or only a few dozen simulations, may have over-looked.

Polar bear in the Arctic. A project running almost 10,000 climate simulations on volunteers’ home computers has found that a global warming of 3 degrees Celsius by 2050 is ‘equally plausible’ as a rise of 1.4 degrees. (Credit: © Jan Will / Fotolia)

Importantly, the forecast range is derived from models that accurately reproduce observed temperature changes over the last 50 years.

The results suggest that the world is very likely to cross the ‘2 degrees barrier’ at some point this century if emissions continue unabated, and that those planning for the impacts of climate change need to consider the possibility of warming of up to 3 degrees (above the 1961-1990 average) by 2050 even on a mid-range emission scenario. This is a faster rate of warming than most other models predict.

A report of the research is published in Nature Geoscience.

‘It’s only by running such a large number of simulations — with model versions deliberately chosen to display a range of behaviour — that you can get a handle on the uncertainty present in a complex system such as our climate,’ said Dr Dan Rowlands of Oxford University’s Department of Physics, lead author of the paper. ‘Our work was only possible because thousands of people donated their home computer time to run these simulations.’

‘Most forecasts of global warming are based on the range of results that different groups around the world happen to contribute to a model comparison. These groups don’t set out to explore the full range of uncertainty, which is why studies like ours are needed,’ said Professor Myles Allen of the School of Geography and Environment and Department of Physics, Oxford University, an author of the paper.

Dr Ben Booth, Senior Climate Scientist at the Met Office Hadley Centre, an author of the paper, said: ‘There have been substantial efforts within the international community to quantify and understand the consequence of climate uncertainties for future projections. Perhaps the most ambitious effort to date, this work illustrates how the citizen science movement is making an important contribution to this field.

‘Co-author Professor Dave Frame of Victoria University of Wellington, Visiting Fellow of Oxford University’s Smith School of Enterprise and the Environment, said: ‘Ensembles like this are an innovative way of exploring a range of possible futures, and provide an exciting new resource for the climate adaptation and impact communities.’

The model used in the project was supplied by the UK Met Office and the work was supported by the Natural Environment Research Council (NERC), the European Union FP6 WATCH and ENSEMBLES projects, the Oxford Martin School, the Smith School of Enterprise and the Environment, and Microsoft Research.

The research was made possible because volunteers donated time to run the simulations on their home computers throughclimateprediction.net as part of the BBC Climate Change Experiment.

Courtesy : BBC

Life Existense possible in Super Earth

While scientists believe conditions suitable for life might exist on the so-called “super-Earth” in the Gliese 581 system, it’s unlikely to be transferred to other planets within that solar system.”One of the big scientific questions is how did life get started and how did it spread through the universe,” said Jay Melosh, distinguished professor of earth and atmospheric sciences. “That question used to be limited to just the Earth, but we now know in our solar system there is a lot of exchange that takes place, and it’s quite possible life started on Mars and came to Earth. There’s also been a great deal of discussion about the possible spread of life in the universe from star to star.”Moon rocks and Mars meteorites have been found on Earth, which led Melosh to previously suggest living microbes could be exchanged among planets in a similar manner.

Planets of the Gliese 581 System. This artist’s conception shows the inner four planets of the Gliese 581 system and their host star, a red dwarf star only 20 light years away from Earth. The large planet in the foreground is the newly discovered GJ 581g, which has a 37-day orbit right in the middle of the star’s habitable zone and is only three to four times the mass of Earth, with a diameter 1.2 to 1.4 times that of Earth. (Credit: Lynette Cook/NASA)

A Purdue research team has found that, in contrast to our own solar system, the exchange of living microbes between “super-Earth” and planets in that solar system is not likely to occur.

Laci Brock, a student studying interdisciplinary physics and planetary science, and Melosh will present those findings March 20 at the 43rd Lunar and Planetary Science Conference in The Woodlands, Texas.

Brock examined the Gliese 581 planetary system because Planet d, known as super-Earth, falls in a “habitable zone” where liquid water could possibly exist.

“Laci has found the somewhat surprising result that it is very difficult for materials to spread throughout that system in the same way it could take place in our solar system,” Melosh said.

All four planets found in Gliese 581 are within close proximity to their central star, which results in large orbital velocities, Brock said. However, the initial velocity of material leaving Planet d is not enough to allow exchanges among planets.

“Planet d would have a very small chance of transferring material to the other planets in the Gliese system and, thus, is far more isolated, biologically, than the inner planets of our own solar system,” Brock said. “It really shows us how unique our solar system is.”

Melosh said a more extended solar system would be needed for exchange of materials among planets.

“None of the solar systems that have been found so far would have opportunities for exchange of life among the different planets like what our own solar system offers,” he said.

The Opik-Arnold method was used to simulate 10,000 particles being ejected from Planet e and super-Earth. The velocity ranges of the particles were scaled from each of the planet’s orbital velocities, which is very high by solar system standards due to the close proximity to their central star.

“Ejections from Planet d have a low probability of impact on any other planet than itself, and most ejected particles would enter an initial hyperbolic orbit and be ejected from the planetary system,” Brock said.

Several members of Purdue’s planetary sciences department are attending the 43rd Lunar and Planetary Science Conference, presenting research on possible biologic contamination of Mars’ moon Phobos by microbes from the surface of Mars; the formation of jets on comets; and gravity anomalies around large lunar craters.

“Purdue has quite a showing of different people at this conference to showcase their work,” Melosh said.