Cracks in Pluto's moon could indicate it once had an underground ocean

This artist concept shows Pluto and some of its moons, as viewed from the surface of one of the moons. Pluto is the large disk at center. Charon is the smaller disk to the right.

If the icy surface of Pluto's giant moon Charon is cracked, analysis of the fractures could reveal if its interior was warm, perhaps warm enough to have maintained a subterranean ocean of liquid water, according to a new NASA-funded study.

Pluto is an extremely distant world, orbiting the sun more than 29 times farther than Earth. With a surface temperature estimated to be about 380 degrees below zero Fahrenheit (around minus 229 degrees Celsius), the environment at Pluto is far too cold to allow liquid water on its surface. Pluto's moons are in the same frigid environment.

Pluto's remoteness and small size make it difficult to observe, but in July of 2015, NASA's New Horizons spacecraft will be the first to visit Pluto and Charon, and will provide the most detailed observations to date.

"Our model predicts different fracture patterns on the surface of Charon depending on the thickness of its surface ice, the structure of the moon's interior and how easily it deforms, and how its orbit evolved," said Alyssa Rhoden of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "By comparing the actual New Horizons observations of Charon to the various predictions, we can see what fits best and discover if Charon could have had a subsurface ocean in its past, driven by high eccentricity." Rhoden is lead author of a paper on this research now available online in the journal Icarus.

Some moons around the gas giant planets in the outer solar system have cracked surfaces with evidence for ocean interiors -- Jupiter's moon Europa and Saturn's moon Enceladus are two examples.

As Europa and Enceladus move in their orbits, a gravitational tug-of-war between their respective parent planets and neighboring moons keeps their orbits from becoming circular. Instead, these moons have eccentric (slightly oval-shaped) orbits, which raise daily tides that flex the interior and stress the surface. It is thought that tidal heating has extended the lifetimes of subsurface oceans on Europa and Enceladus by keeping their interiors warm.

In Charon's case, this study finds that a past high eccentricity could have generated large tides, causing friction and surface fractures. The moon is unusually massive compared to its planet, about one-eighth of Pluto's mass, a solar system record. It is thought to have formed much closer to Pluto, after a giant impact ejected material off the planet's surface. The material went into orbit around Pluto and coalesced under its own gravity to form Charon and several smaller moons.

Initially, there would have been strong tides on both worlds as gravity between Pluto and Charon caused their surfaces to bulge toward each other, generating friction in their interiors. This friction would have also caused the tides to slightly lag behind their orbital positions. The lag would act like a brake on Pluto, causing its rotation to slow while transferring that rotational energy to Charon, making it speed up and move farther away from Pluto.

"Depending on exactly how Charon's orbit evolved, particularly if it went through a high-eccentricity phase, there may have been enough heat from tidal deformation to maintain liquid water beneath the surface of Charon for some time," said Rhoden. "Using plausible interior structure models that include an ocean, we found it wouldn't have taken much eccentricity (less than 0.01) to generate surface fractures like we are seeing on Europa."

"Since it's so easy to get fractures, if we get to Charon and there are none, it puts a very strong constraint on how high the eccentricity could have been and how warm the interior ever could have been," adds Rhoden. "This research gives us a head start on the New Horizons arrival -- what should we look for and what can we learn from it. We're going to Pluto and Pluto is fascinating, but Charon is also going to be fascinating."

Based on observations from telescopes, Charon's orbit is now in a stable end state: a circular orbit with the rotation of both Pluto and Charon slowed to the point where they always show the same side to each other. Its current orbit is not expected to generate significant tides, so any ancient underground ocean may be frozen by now, according to Rhoden.

Since liquid water is a necessary ingredient for known forms of life, the oceans of Europa and Enceladus are considered to be places where extraterrestrial life might be found. However, life also requires a useable energy source and an ample supply of many key elements, such as carbon, nitrogen, and phosphorus. It is unknown if those oceans harbor these additional ingredients, or if they have existed long enough for life to form. The same questions would apply to any ancient ocean that may have existed beneath the icy crust of Charon.

This research was funded by the NASA Postdoctoral Program at the NASA Goddard Space Flight Center, administered by Oak Ridge Associated Universities, and NASA Headquarters through the Science Innovation Fund.

Planet bonanza hints at worlds similar to our own

A team of astronomers has used data from NASA’s Kepler space telescope to uncover 715 new exoplanets and the first Earth-sized planet in the habitable zone of its star, Kepler-186f, this year.

The artist concept depicts multiple-transiting planet systems, which are stars with more than one planet. The planets eclipse or transit their host star from the vantage point of the observer. This angle is called edge-on.

For planet hunters, this has been a bountiful year. A team of astronomers at the SETI Institute in Mountain View, California, and NASA Ames Research Center in Moffett Field, California, has used data from NASA's Kepler space telescope to uncover 715 new exoplanets. The newly verified objects orbit 305 different stars and therefore include multiworld systems that are reminiscent of the Sun's planetary family. The announcement of these discoveries was followed by news that Kepler had also found the first Earth-sized planet in the habitable zone of its star, Kepler-186f. This is a significant milestone in the task of determining the prevalence of terrestrial planets in the Milky Way Galaxy.

"These results are showing us that not only are Earth-sized planets common, but so are multiplanet systems containing potentially habitable worlds," said Jason Rowe from the SETI Institute. "Most of the new planets orbit their host star much closer than Mercury, but a few are beginning to bear a similarity to our own solar system."

The deluge of new planets has been intensified by a new analysis scheme called verification by multiplicity. This technique can be applied to many planets at once, allowing the researchers to verify hundreds of new planetary systems in wholesale fashion, rather than teasing them from the Kepler data one-by-one as done in the past. The new technique uses probability arguments based on the recognition that, of the 150,000 stars observed by Kepler, hundreds were found that have multiple planet candidates. On this basis, the researchers are assured that their results are not distorted by binary stars that can mimic a multiworld system. The new discoveries increase the total number of known exoplanets to over 1,700.

"From this work, we've also learned that planets in these multiple systems are small, and their orbits are flat and circular, much like our own solar system," Rowe said.

On April 17, the Kepler team announced the discovery of Kepler-186f, the first Earth-sized planet found in the habitable zone of its host star, marking a major milestone in determining the frequency of Earth-like planets in the Milky Way Galaxy.

"Uncovering these worlds and showing that habitable worlds could be very common has increased the likelihood that there is life — perhaps abundant life — elsewhere in the cosmos," said David Black from the SETI Institute.

Data collection from the Kepler mission ended in the spring of last year due to the failure of a second onboard reaction wheel, essential to accurate pointing of the telescope. However, on May 20, NASA announced the approval of the K2 mission, which intended to repurpose Kepler to use the pressure of sunlight hitting the side of the spacecraft to act as a third wheel.

"We can't continue to look at the original Kepler star field," said Douglas Caldwell from the SETI Institute, "but spacecraft are built and operated by very smart people, and thanks to the hard work of the entire Kepler team, we can now search for planets in a wide variety of environments and conditions, including star forming regions. Doing so will teach us more about how our own planetary system formed and evolved."

"The more we explore, the more we find worlds among the stars that remind us of home," Rowe said.

Milky Way may bear 100 million life-giving planets

There are some 100 million other places in the Milky Way galaxy that could support complex life, report a group of university astronomers in the journal Challenges. They have developed a new computation method to examine data from planets orbiting other stars in the universe.

A new computation method to examine planets orbiting other stars suggests the Milky Way galaxy may house 100 million other places that could support complex life.

Their study provides the first quantitative estimate of the number of worlds in our galaxy that could harbor life above the microbial level.

"This study does not indicate that complex life exists on that many planets. We're saying that there are planetary conditions that could support it. Origin of life questions are not addressed -- only the conditions to support life," according to the paper's authors Alberto Fairén, Cornell research associate; Louis Irwin, University of Texas at El Paso (lead author); Abel Méndez, University of Puerto Rico at Arecibo; and Dirk Schulze-Makuch, Washington State University.

"Complex life doesn't mean intelligent life -- though it doesn't rule it out or even animal life -- but simply that organisms larger and more complex than microbes could exist in a number of different forms. For example, organisms that form stable food webs like those found in ecosystems on Earth," the researchers explain in an auxiliary statement.

The scientists surveyed more than 1,000 planets and used a formula that considers planet density, temperature, substrate (liquid, solid or gas), chemistry, distance from its central star and age. From this information, they developed and computed the Biological Complexity Index (BCI).

The BCI calculation revealed that 1 to 2 percent of the planets showed a BCI rating higher than Europa, a moon of Jupiter thought to have a subsurface global ocean that may harbor forms of life. With about 10 billion stars in the Milky Way galaxy, the BCI yields 100 million plausible planets.

Despite the large number of planets that could harbor complex life, the Milky Way is so vast that planets with high BCI values are very far apart, according to the scientists. One of the closest and most promising extrasolar systems, called Gliese 581, has two planets with the apparent, possible capacity to host complex biospheres. The distance from Earth to Gliese 581 is about 20 light years.

"It seems highly unlikely that we are alone," say the researchers. "We are likely so far away from life at our level of complexity that a meeting with such alien forms might be improbable for the foreseeable future."

The research, "Assessing the Possibility of Biological Complexity on Other Worlds, With an Estimate of the Occurrence of Complex Life in the Milky Way Galaxy," inChallenges, received no external funding.

'Hello, world!' NASA beams video from space station via laser

"Helllo, World!" came the message from the International Space Station as NASA successfully beamed high-definition video via laser from space to ground on Thursday, June 5. The 175-megabit video transmission was the first of its kind for the Optical Payload for Lasercomm Science (OPALS) with the goal of improving the way we receive data from orbit and beyond. In fact, this emerging technology of optical communications--or lasercomm--is likened to an upgrade from dial-up to DSL.

This artist's concept shows how the Optical Payload for Lasercomm Science (OPALS) laser beams data to Earth from the International Space Station.

"It's incredible to see this magnificent beam of light arriving from our tiny payload on the space station," said Matt Abrahamson, OPALS mission manager at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.

OPALS launched to the space station aboard the SpaceX Dragon earlier this spring. This technology demonstration furthers NASA's exploration of higher-bandwidth methods of communicating with future spacecraft. Optical communications tools like OPALS use focused laser energy to achieve data rates 10 to 1,000 times higher than current space communications, which rely on radio portions of the electromagnetic spectrum.

OPALS' success also is an important step in improving communication rates with spacecraft beyond low-Earth orbit. The instrument allows for communications rates to keep pace with the ever-increasing data generation produced by scientific instruments. The capability could replace the Federally-regulated radio frequencies currently in use from orbit to meet the needs anticipated by researchers for future missions, like Mars.

"We look forward to experimenting with OPALS over the coming months in hopes that our findings will lead to optical communications capabilities for future deep space exploration missions," Abrahamson said.

The space station moves through Earth's sky at approximately 17,500 mph. This speed requires extreme precise pointing ability. It's equivalent to a person aiming a laser pointer at the end of a human hair 30 feet away and keeping it there while walking. To achieve this precision, OPALS locked onto a ground beacon emitted by the Optical Communications Telescope Laboratory ground station at the Table Mountain Observatory in Wrightwood, California.

Once locked onto the signal, OPALS began to modulate the beam from its 2.5-Watt 1,550-nanometer laser to transmit the video. The entire transmission lasted 148 seconds and achieved a maximum data rate of 50 megabits per second. It took OPALS 3.5 seconds to transmit a single copy of the "Hello World!" video message, which would have taken more than 10 minutes using traditional downlink methods. The message was sent multiple times during the transmission.

The OPALS instrument was built at JPL as part of the Phaeton hands-on training program and is slated to run for a prime mission of 90 days. The OPALS Project Office is based at JPL, a division of the California Institute of Technology in Pasadena. During these transmissions, NASA also will train personnel in optical communication systems operations, leading to improved optical communication instrument design.

Commercial ventures can likewise take note of the project, as it proves the use of lasercomm for optimized communications from space. This may mean higher definition video feeds from near-Earth assets, such as satellites, as well as those in deep space, like future Mars rovers. This improves the interaction and experience with the stakeholders, whether they be researchers, engineers or consumers. And if you remember the days of having to leave the room to download a video when using DSL, you know that higher-speed downloads are definitely the way to go!

Chandra captures galaxy sparkling in X-rays

A decade of Whirlpool Galaxy observations provide critical information about how X-ray sources containing black holes behave over time.

A new Chandra image of M51 contains nearly a million seconds of observing time. The data reveal hundreds of point-like X-ray sources within what is nicknamed the "Whirlpool Galaxy." Most of these point sources are X-ray binary systems with either a neutron star or black hole orbiting a Sun-like star. The composite image consists of X-rays from Chandra (purple) and optical data from Hubble (red, green, and blue).

Nearly a million seconds of observing time with NASA’s Chandra X-ray Observatory has revealed a spiral galaxy similar to the Milky Way, glittering with hundreds of X-ray points of light.

The galaxy is officially named Messier 51 (M51) or NGC 5194 but often goes by its nickname of the “Whirlpool Galaxy.” Like the Milky Way, the Whirlpool is a spiral galaxy with spectacular arms of stars and dust. M51 is located 30 million light-years from Earth, and its face-on orientation to Earth gives us a perspective that we can never get of our own spiral galactic home.

By using Chandra, astronomers can peer into the Whirlpool to uncover things that can only be detected in X-rays. In this new composite image, Chandra data are shown in purple. Optical data from the Hubble Space Telescope are red, green, and blue.

Most of the X-ray sources are X-ray binaries (XRBs). These systems consist of pairs of objects where a compact star, either a neutron star or, more rarely, a black hole, is capturing material from an orbiting companion star. The infalling material is accelerated by the intense gravitational field of the compact star and heated to millions of degrees, producing a luminous X-ray source. The Chandra observations reveal that at least 10 of the XRBs in M51 are bright enough to contain black holes. In eight of these systems, the black holes are likely capturing material from companion stars that are much more massive than the Sun.

Because astronomers have been observing M51 for about a decade with Chandra, they have critical information about how X-ray sources containing black holes behave over time. The black holes with massive stellar companions are consistently bright over the 10 years of Chandra observations. These results suggest that the high-mass stars in these X-ray sources also have strong winds that allow for a steady stream of material to flow onto the black hole.

A difference between the Milky Way and the Whirlpool Galaxy is that M51 is in the midst of merging with a smaller companion galaxy seen in the upper left of the image. Scientists think this galactic interaction is triggering waves of star formation. The most massive of the newly formed stars will race through their evolution in a few million years and collapse to form neutron stars or black holes. Most of the XRBs containing black holes in M51 are located close to regions where stars are forming, showing their connection to the oncoming galactic collision.

Previous studies of the Whirlpool Galaxy with Chandra revealed just over 100 X-ray sources. The new data set, equivalent to about 900,000 seconds of Chandra observing time, reveals nearly 500 X-ray sources. About 400 of these sources are thought to be within M51, with the remaining either being in front of or behind the galaxy itself.

Much of the diffuse, or fuzzy, X-ray emission in M51 comes from gas that has been superheated by supernova explosions of massive stars.