Laboratory models suggest that stretching forces shaped Ganymede's surface

An image of a tabletop-size analogue model (left) shows details of fault systems created by extension that visually match an image by spacecraft Galileo of faulted terrain on Ganymede (right). 

Credit: Left Image: Courtesy of Southwest Research Institute; 

Right Image: Courtesy of NASA/JPL SSI

Processes that shaped the ridges and troughs on the surface of Jupiter's icy moon Ganymede are likely similar to tectonic processes seen on Earth, according to a team of researchers led by Southwest Research Institute (SwRI).

To arrive at this conclusion, the team subjected physical models made of clay to stretching forces that simulate tectonic action. The results were published in Geophysical Research Letters.

Physical analogue models simulate geologic structures in laboratory settings so that the developmental sequence of various phenomena can be studied as they occur.

The team, including researchers from SwRI, Wheaton College, NASA's Jet Propulsion Laboratory and NuStar Energy LP, created complex patterns of faults in their models, similar to the ridge and trough features seen in some regions of Ganymede.

The models consisted of a "wet clay cake" material possessing brittle characteristics to simulate how the icy moon's lithosphere, the outermost solid shell, responds to stresses by cracking.

The laboratory models suggest that characteristic patterns of ridges and troughs, called grooved terrain on Ganymede, result from its surface being stretched.

"The physical models showed a marked similarity to the surface features observed on Ganymede," said co-author Dr. Danielle Wyrick, a senior research scientist in the SwRI Space Science and Engineering Division.

"From the experiments, it appears that a process in which the crust breaks into separate blocks by large amounts of extension is the primary mechanism for creating these distinct features."

"Physical analogue modeling allows us to simulate the formation of complex three-dimensional geological structures on Ganymede, without actually going to Ganymede," said co-author Dr. David Ferrill, director of the Earth, Material and Planetary Sciences Department in the SwRI Geosciences and Engineering Division.

"These scaled models are able to reproduce the fine geometric details of geologic processes, such as faulting, and to develop and test hypotheses for landscape evolution on planetary bodies."

SwRI researchers previously have used physical analog models to examine the process by which pit crater chains, a series of linear pits, or depressions, develop on Mars, and how magma in the Martian subsurface deforms the surface of the Red Planet.

More information: The paper, "Physical models of grooved terrain tectonics on Ganymede," by D.W. Sims, D.Y. Wyrick, D.A. Ferrill, A.P. Morris, G.C. Collins, R.T. Pappalardo and S.L. Colton, was published by Geophysical Research Letters, 16 June 2014, Volume 41, Issue 11, pages 3774–3778, DOI: 10.1002/2014GL060359

SwRI chosen by NASA to study solar particles and space weather CuSPP

NASA has selected Southwest Research Institute (SwRI) to develop CuSPP, a CubeSat mission to study Solar Particles over the Earth's Poles. SwRI will also lead mission science operations and data analysis.

During the five-year project, engineers and scientists will design, develop and integrate a CubeSat, a nano-satellite launched as a secondary payload on another satellite mission, carrying a novel miniaturized Suprathermal Ion Sensor (SIS) developed at SwRI.

The SIS will measure the sources and acceleration mechanisms of solar energetic particles that are harmful to astronauts as well as Earth-based technologies.

CuSPP can also be used to support space weather research by measuring particles that escape ahead of powerful shock waves in the solar wind.

Upon striking the Earth, solar particles and shock waves can cause severe electromagnetic storms, damage satellites, disrupt radio communication and navigation signals, damage electric power grids and corrode pipelines.

In addition, CuSPP is designed to measure the properties of ion populations entering the ionosphere, the uppermost portion of the Earth's atmosphere.

"Upon successful completion, we expect CuSPP to have achieved several key goals, such as increasing the technological readiness level and reducing the risks and costs of flying a new class of SwRI science instruments for studying heliophysics, the Sun's effects on the solar system," says Dr. Mihir Desai, CuSPP principal investigator and a staff scientist in the SwRI Space Science and Engineering Division.

"We also expect to provide critical measurements that shed light on the origins of hazardous charged particle populations accelerated at the Sun and interplanetary space, as well as play a major role in developing reliable nano-satellites for NASA and other sponsors."

CuSPP will fly as a secondary payload as early as 2017. It will reside in a high-inclination (> 65 degrees) low-Earth orbit, approximately 500 km above Earth, for the duration of its mission.

The primary satellite on which CuSPP will launch will be named at a later date.

The CubeSat concept was developed in 1999 as an academic tool to provide students with an inexpensive way to gain hands-on experience in designing and building satellites.

More recently, they have been used for scientific research, exploration, technology development and operations.

A standard CubeSat is a 10 centimeter cube with a one-liter volume. CuSPP is 30 by 10 by 10 centimeters with a volume of three liters.

NASA has increased the reliability and functionality of CubeSats to extend the use of this miniaturized platform into deep space.

The agency recently implemented a new CubeSat initiative for its Science Mission Directorate (SMD).

SwRI is collaborating with the NASA Goddard Space Flight Center, Greenbelt, Md., to produce the CubeSat, including the flight segment (integrated at SwRI), ground segment (provided by the NASA Wallops Flight Facility) and payload (developed at SwRI).

CuSPP was selected as part of the 2013 Heliophysics-Technology and Instrument Development for Science (H-TIDeS) 2013 competition, with funding from the new NASA SMD-wide CubeSat initiative managed by NASA's Heliophysics Division.

KOI-314c: Newfound planet is Earth-mass but gassy

KOI-314c, shown in this artist's conception, is the lightest planet to have both its mass and physical size measured. 

Surprisingly, although the planet weighs the same as Earth, it is 60 percent larger in diameter, meaning that it must have a very thick, gaseous atmosphere. 

It orbits a dim, red dwarf star (shown at left) about 200 light-years from Earth. 

KOI-314c interacts gravitationally with another planet, KOI-314b (shown in the background), causing transit timing variations that allow astronomers to measure the masses of both worlds. 

This serendipitous discovery resulted from analysis as part of the Hunt for Exomoons with Kepler (HEK) project. 

Credit: C. Pulliam & D. Aguilar (CfA)

An international team of astronomers has discovered the first Earth-mass planet that transits, or crosses in front of, its host star.

KOI-314c is the lightest planet to have both its mass and physical size measured. Surprisingly, although the planet weighs the same as Earth, it is 60 percent larger in diameter, meaning that it must have a very thick, gaseous atmosphere.

"This planet might have the same mass as Earth, but it is certainly not Earth-like," says David Kipping of the Harvard-Smithsonian Center for Astrophysics (CfA), lead author of the discovery.

"It proves that there is no clear dividing line between rocky worlds like Earth and fluffier planets like water worlds or gas giants."

Kipping presented this discovery today in a press conference at the 223rd meeting of the American Astronomical Society.

The team gleaned the planet's characteristics using data from NASA's Kepler spacecraft. KOI-314c orbits a dim, red dwarf star located approximately 200 light-years away.

It circles its star every 23 days. The team estimates its temperature to be 220 degrees Fahrenheit, too hot for life as we know it.

KOI-314c is only 30 percent denser than water. This suggests that the planet is enveloped by a significant atmosphere of hydrogen and helium hundreds of miles thick.

It might have begun life as a mini-Neptune and lost some of its atmospheric gases over time, boiled off by the intense radiation of its star.

Weighing such a small planet was a challenge. Conventionally, astronomers measure the mass of an exoplanet by measuring the tiny wobbles of the parent star induced by the planet's gravity.

This radial velocity method is extremely difficult for a planet with Earth's mass. The previous record holder for a planet with a measured mass (Kepler-78b) weighed 70 percent more than Earth.

To weigh KOI-314c, the team relied on a different technique known as transit timing variations (TTV). This method can only be used when more than one planet orbits a star.

The two planets tug on each other, slightly changing the times that they transit their star.

David Nesvorny

"Rather than looking for a wobbling star, we essentially look for a wobbling planet," explains second author David Nesvorny of the Southwest Research Institute (SwRI).

"Kepler saw two planets transiting in front of the same star over and over again. By measuring the times at which these transits occurred very carefully, we were able to discover that the two planets are locked in an intricate dance of tiny wobbles giving away their masses."

The second planet in the system, KOI-314b, is about the same size as KOI-314c but significantly denser, weighing about 4 times as much as Earth.

It orbits the star every 13 days, meaning it is in a 5-to-3 resonance with the outer planet.

TTV is a very young method of finding and studying exoplanets, first used successfully in 2010. This new measurement shows the potential power of TTV, particularly when it comes to low-mass planets difficult to study using traditional techniques.

"We are bringing transit timing variations to maturity," adds Kipping.

The planet was discovered by chance by the team as they scoured the Kepler data not for exoplanets, but for exomoons.

The Hunt for Exomoons with Kepler (HEK) project, led by Kipping, scans through Kepler's planet haul looking for TTV, which can also be a signature of an exomoon.

"When we noticed this planet showed transit timing variations, the signature was clearly due to the other planet in the system and not a moon. At first we were disappointed it wasn't a moon but then we soon realized it was an extraordinary measurement," says Kipping.

First detection of a predicted unseen exoplanet

Artist impression of the Kepler-88 system. 

Credit: Alexandre Santerne (CAUP)/ESO/Serge Brunier

A team of European astronomers, including EXOEarths member Alexandre Santerne (CAUP), used the SOPHIE spectrograph at the Observatoire de Haute-Provence (France), to confirm the presence of Kepler-88 c, an unseen planet that was previously predicted thanks to the gravitational perturbation it caused on its transiting brother planet, Kepler-88 b.

Searching for periodic transits in hundreds of thousands of stars was the primary goal of the Kepler space telescope. More than 3,500 of such periodic transits were found during the 4 years of the mission.

However, not all the planets located in the Kepler field-of-view are transiting their host star. Indeed, if their orbital plane is slightly misaligned (only a few degrees is enough) with the line of sight from the Earth, the planet is not transiting and, thus, is "unseen" from the Kepler spacecraft.

Planets that share the same host star gravitationally interact with each other. This interaction between planets can cause perturbations in the predicted times of transit of planets in multi-planetary systems.

"This is called transit timing variations (TTV)" explains the leading author of the paper, Susana Barros, a researcher at the Laboratoire d'Astrophysique de Marseille (LAM).

The TTV technique is sensitive to planets in multiple systems down to the mass of the Earth, and can therefore be used to unveil the existence of non-transiting planets, that cause perturbations in the orbital motion of transiting planets.

This is the case of the Kepler-88 system, which hosts a transiting planet (Kepler-88 b), discovered by the Kepler space telescope (NASA) , that is strongly perturbed by a non-transiting planet (Kepler-88 c).

"This system presents such strong interactions that it has earned the nickname of the king of transit variations" adds Rodrigo Diaz, a researcher working at the Geneva Observatory (OAUG).

Picture of the dome of the 1.93-m telescope of Haute-Provence Observatory (France) which hosts the SOPHIE spectrograph, with the Kepler field-of-view. 

Credit: Alexandre Santerne (CAUP)

A careful analysis of the dynamical interaction between planets, previously performed by a team led by David Nesvorny (Southwest Research Institute), predicted that this system had two planets near a two-to-one resonance (the orbital period of the unseen outer planet is exactly two times longer than the transiting inner planet).

This configuration is similar to the Earth and Mars in the solar system, with Mars orbiting the Sun in nearly 2 years.

Using the SOPHIE velocimeter, the team independently measured the mass of Kepler-88 c.

"SOPHIE is a French instrument capable of measuring the velocity of stars with a precision equivalent to the speed of a bicycle.

It has been used to characterize nearly 20 Kepler planets so far" adds Alexandre Santerne a researcher at Centro de Astrofísica da Universidade do Porto (CAUP) and responsible of the observations of Kepler targets with SOPHIE.

The article "SOPHIE Velocimetry of Kepler Transit Candidates X KOI-142c: First Radial Velocity Confirmation of a Non-Transiting Exoplanet Discovered by Transit Timing," is published 17 December 2013 in Astronomy & Astrophysics: dx.doi.org/10.1051/0004-6361/201323067

NASA Curiosity Rover: Radiation on Mars 'Manageable' for Manned Mission

The risk of radiation exposure is not a show-stopper for a long-term manned mission to Mars, new results from NASA's Curiosity rover suggest.

A mission consisting of a 180-day cruise to Mars, a 500-day stay on the Red Planet and a 180-day return flight to Earth would expose astronauts to a cumulative radiation dose of about 1.01 sieverts, measurements by Curiosity's Radiation Assessment Detector (RAD) instrument indicate.

To put that in perspective: The European Space Agency generally limits its astronauts to a total career radiation dose of 1 sievert, which is associated with a 5-percent increase in lifetime fatal cancer risk.

Radiation Assessment Detector

About the size of a small toaster, the Radiation Assessment Detector will look skyward and use a stack of silicon detectors and a crystal of cesium iodide to measure galactic cosmic rays and solar particles that pass through the Martian atmosphere. 

Image credit: NASA/JPL-Caltech/SwRI

Pluto satellites' orbital ballet may hint of long-ago collisions

A best-fit colour image/map of Pluto generated with the Hubble Space Telescope and advanced computers. Image: NASA

A large impact 4 billion years ago may account for the puzzling orbital configuration among Pluto's five known satellites, according to a new model developed by planetary scientists from Southwest Research Institute (SwRI).

Starting with Charon, Pluto's nearest and largest moon, each of the successively more distant—and much smaller—moons orbits Pluto according to a steadily increasing factor of Charon's own orbital period.

The small satellites, Styx, Nix, Kereberos and Hydra, have orbital periods that are almost exactly 3, 4, 5 and 6 times longer than Charon's.

Harold "Hal" Levison

"Their distance from Pluto and the orbital arrangement of the satellites has been a challenge for theories of the small satellites' formation," said lead investigator Dr. Harold "Hal" Levison, an Institute scientist in SwRI's Planetary Science Directorate at Boulder, Colo.

Models for the formation of Charon leave plenty of small satellites, but all of them are much closer to Pluto than the current system that we see today," said Levison.

A major problem has been understanding how to move these satellites outward, but not lose them from the Pluto-Charon system or have them crash into Charon.

He said, "This configuration suggests that we have been missing some important mechanism to transport material around in this system."

The SwRI study, funded by a grant from NASA's Outer Planetary Research program and Lunar Science Institute, considered the earliest and most dynamic epoch of the Pluto/Charon system.

It is thought that Charon was formed by a large impact during a period in solar system history when such collisions were dramatically more frequent.

Pluto's moon Charon

Any initially surviving satellites would likely be destroyed in collisions, but these shattered moons wouldn't be lost; rather, their remains would stay in the Pluto/Charon system and become the starting point for building new satellites.

Thus there would have been many generations of satellite systems over the history of Pluto and Charon.

In modeling the destruction of the satellites, the SwRI study found that there may be a method for moving them, or their building blocks, outward, due to the competing effects of Charon's gravitational kicks and collisions among the debris of the disrupted satellites.

Charon is the largest satellite of any planet or dwarf-planet, weighing in at 1/10 the mass of Pluto (the Moon is just 1/81 the mass of Earth), and so it could rapidly slingshot the small satellites outward if they were to approach too closely.

Kevin Walsh

Meanwhile, collisions among small satellites can change orbits to keep things away from Charon. When combined, this leads to a series of satellites colliding, breaking to pieces, moving outward and then rebuilding.

"The implications for this result are that the current small satellites are the last generation of many previous generations of satellites," said Dr. Kevin Walsh, another investigator and a research scientist in SwRI's Planetary Science Directorate at Boulder, Colo.

"They were probably first formed around 4 billion years ago, and after an eventful million years of breaking and rebuilding, have survived in their current configuration ever since."

ESA Mars Express: 10 years on, Europe salutes its Martian scout

Mars Express. Credits: Alex Lutkus

It was built on a relative shoestring, was completed in just five years and was designed to survive for just 687 days.

Ten years later, after more than 12,000 swings around the Red Planet, Europe's Mars Express is still going strong.

Along with NASA's massively successful fleet of probes and landers, the orbital scout has helped pull aside the veil of secrecy surrounding our sister planet.

It has pointed to the presence of subterranean water and a wild volcanic past and shed light on the bizarrely-pocked martian moons.

"The mission has already provided countless breathtaking views of Mars in three dimensions," says the European Space Agency (ESA).

"It has traced the history of water across the globe, demonstrating that Mars once harboured environmental conditions that may have been suitable for life."

The orbiter's seven instruments have detected minerals that form only in the presence of water and seen underground formations of water ice. Scans of the surface suggest volcanism on Mars may have persisted until recent times.

And its chemical analysis of the martian atmosphere indicates the possible presence of methane—which on Earth is attributed to active volcanism and biological life.

The first European mission to explore another planet, Mars Express was launched from Baikonur cosmodrome by a Russian Soyuz rocket on June 2 2003, just when Earth and Mars were approaching their closest alignment in 17 years.

The mission ran into a humiliating setback that December with the crash of a small British-built lander, Beagle-2, whose loss remains unexplained to this day.

But the mission, designed to last for one martian year, has already been extended four times, and its latest closure date is for the end of 2014.

ESA ExoMars

Mars Express is proving to be so sturdy that its builder, EADS Astrium, believes it may even be around in January 2016 to welcome ESA ExoMars, an unmanned European-Russian mission that will explore the methane enigma.

"Nobody would have believed it back then," says the German Aerospace Center (DLR), which developed what is arguably the star instrument aboard Mars Express: a stereoscopic camera that has imaged more than two-thirds of the planet in colour and 3D to a resolution of 20 metres (65 feet) per pixel.

Memorable images include Mars' icy southern pole and Olympus Mons which towers 26,000 metres (84,500 feet) above the surrounding plains.

Conceived as a streamlined, low-cost project, Mars Express was a gamble for ESA.

It broke with conventional thinking that planetary exploration required individually-tailored probes that took a decade to make and inevitably cost a billion bucks apiece.

To save costs, ESA's contractors essentially resorted to mass production.

ESA Rosetta

The basic box-like design for Mars Express, and for a sister spacecraft called Venus Express—launched in 2005 and also doing fine—is the same platform as for Rosetta, a comet-chasing probe whose mission is due to climax next year.

So far, exploration of Mars has cost ESA 300 million euros ($390 million), which is minute for a mission that has returned such wonders, and not a single life has been placed at risk.

Last week came proof that a manned trip to Mars would be health-threatening unless today's chemical rockets are replaced by much faster transport.

Measurements made aboard the Mars Science Laboratory, an unmanned NASA rover and mobile lab that landed in August 2012 showed exposure to high levels of radiation during its 253-day trip.

These are particles spewed out by the Sun, or coming from beyond our Solar System, that can slice through DNA and boost the risk of cancer.

Cary Zeitlin

"In terms of accumulated dose, it's like getting a whole-body CT scan once every five or six days," said Cary Zeitlin of the Southwest Research Institute's (SwRI) Space Science and Engineering Division.

"Radiation exposure at the level we measured is right at the edge, or possibly over the edge of what is considered acceptable in terms of career exposure limits defined by NASA and other space agencies."

Researchers calculate radiation exposure associated with journey to Mars

The RAD instrument measures radiation dose using silicon detector and plastic scintillator technology.

The latter has a composition somewhat similar to tissue and is more sensitive to neutrons than are the silicon detectors.

This illustration of RAD shows the silicon detectors (A, B & C) that measure charged particles and the plastic detectors (D, E & F) that measure both charged and neutral particles.

Credit: Hassler et al., 2012. Space Science Reviews, 170, 503.

On November 26, 2011, the Mars Science Laboratory began a 253-day, 560-million-kilometer journey to deliver the Curiosity rover to the Red Planet.

Radiation Assessment Detector

En route, the Southwest Research Institute (SwRI) Radiation Assessment Detector (RAD) made detailed measurements of the energetic particle radiation environment inside the spacecraft, providing important insights for future human missions to Mars.

Cary Zeitlin

"In terms of accumulated dose, it's like getting a whole-body CT scan once every five or six days," said Dr. Cary Zeitlin, a principal scientist in SwRI's Space Science and Engineering Division and lead author of Measurements of Energetic Particle Radiation in Transit to Mars on the Mars Science Laboratory, scheduled for publication in the journal Science on May 31.

"Understanding the radiation environment inside a spacecraft carrying humans to Mars or other deep space destinations is critical for planning future crewed missions," Zeitlin said.

"Based on RAD measurements, unless propulsion systems advance rapidly, a large share of mission radiation exposure will be during outbound and return travel, when the spacecraft and its inhabitants will be exposed to the radiation environment in interplanetary space, shielded only by the spacecraft itself."

Two forms of radiation pose potential health risks to astronauts in deep space: a chronic low dose of galactic cosmic rays (GCRs) and the possibility of short-term exposures to the solar energetic particles (SEPs) associated with solar flares and coronal mass ejections.

Radiation dose is measured in units of Sievert (Sv) or milliSievert (1/1000 Sv). Long-term population studies have shown that exposure to radiation increases a person's lifetime cancer risk; exposure to a dose of 1 Sv is associated with a 5 percent increase in fatal cancer risk.

GCRs tend to be highly energetic, highly penetrating particles that are not stopped by the modest shielding provided by a typical spacecraft.

These high-energy particles include a small percentage of so-called heavy ions, which are atomic nuclei without their usual complement of electrons.

Heavy ions are known to cause more biological damage than other types of particles.

Energetic protons constitute about 85 percent of the primary galactic cosmic ray flux and easily traverse even the most shielded paths (reds) inside the MSL spacecraft.

Heavy ions tend to break up into lighter ions in thick shielding, but can survive traversal of thin shielding (blues) intact.

The solar particles of concern for astronaut safety are typically protons with kinetic energies up to a few hundred MeV (one MeV is a million electron volts).

Solar events typically produce very large fluxes of these particles, as well as helium and heavier ions, but rarely produce higher-energy fluxes similar to GCRs.

The comparatively low energy of typical SEPs means that spacecraft shielding is much more effective against SEPs than GCRs.

"A vehicle carrying humans into deep space would likely have a 'storm shelter' to protect against solar particles. But the GCRs are harder to stop and, even an aluminum hull a foot thick wouldn't change the dose very much," said Zeitlin.

"The RAD data show an average GCR dose equivalent rate of 1.8 milliSieverts per day in cruise. The total during just the transit phases of a Mars mission would be approximately .66 Sv for a round trip with current propulsion systems," said Zeitlin.

Time spent on the surface of Mars might add considerably to the total dose equivalent, depending on shielding conditions and the duration of the stay.

Exposure values that ensure crews will not exceed the various space agencies standards are less than 1 Sv.

More Information here