Pluto Reveals Itself
A mere 5 months after New Horizons’ flyby of Pluto on July 14, 2015, Pluto system discoveries—ranging from possible ice volcanoes to oddly behaving moons that could have formed through mergers of smaller moons—continue to surprise scientists on the mission team. Built and operated by APL, NASA’s New Horizons spacecraft travelled 9 years and 3 billion miles to Pluto. Pluto, with its surprising heart-shaped region, has both engaged and delighted its worldwide audience, who waited years to see the dwarf planet.
The extreme distance to Pluto requires patience on the part of eager scientists because only a partial glimpse of the data has been received so far. However, the data received to date have been astounding. The New Horizons team presented some of the data and dozens of reports on exciting discoveries and findings during the 47th Meeting of the Division for Planetary Sciences (DPS) of the American Astronomical Society (AAS) on Nov. 9–13 in National Harbor, Md.
“It’s hard to imagine how rapidly our view of Pluto and its moons is evolving as new data stream in each week. As the discoveries pour in from those data, Pluto is becoming a star of the solar system,” said mission Principal Investigator Alan Stern of the Southwest Research Institute, Boulder, Colo. “Moreover, I’d wager that for most planetary scientists, any one or two of our latest major findings on one world would be considered astounding. To have them all is simply incredible.”
In one such discovery, New Horizons geologists have combined images of Pluto’s surface to make 3-D maps that indicate that two of Pluto’s most distinctive mountains could be cryovolcanoes—ice volcanoes that may have been active in the recent geological past.
Two candidate cryovolcanoes measure tens of miles (tens of kilometers) across and several miles or kilometers high. “These are big mountains with a large hole in their summit, and on Earth that generally means one thing—a volcano,” said Oliver White, New Horizons postdoctoral researcher with NASA’s Ames Research Center, Moffett Field, Calif. Although their appearance is similar to volcanoes on Earth that spew molten rock, ice volcanoes on Pluto would be expected to spew a melted slurry of substances such as water ice, nitrogen, ammonia, or methane.
The interpretation of these features as volcanoes is tentative, reminds White. However, “If they are volcanic, then the summit depression would likely have formed via collapse as material is erupted from underneath. The strange hummocky texture of the mountain flanks may represent volcanic flows of some sort that have travelled down from the summit region and onto the plains beyond, but why they are hummocky, and what they are made of, we don’t yet know.”
“The New Horizons mission has taken what we thought we knew about Pluto and turned it upside down,” said Jim Green, director of planetary science at NASA Headquarters in Washington, D.C. “It’s why we explore—to satisfy our innate curiosity and answer deeper questions about how we got here and what lies beyond the next horizon.”
Burning Questions: How Old Are You?
Another of the more surprising findings from New Horizons is the wide range of surface ages found on Pluto, from ancient to intermediate to relatively young in geological terms. Crater counts used to determine surface unit ages indicate that Pluto has ancient surface areas dating to just after the formation of the planets, about 4 billion years ago. In addition, there is a vast area that was geologically born “yesterday,” meaning it may have formed within the past 10 million years. This area—informally named Sputnik Planum—appears on the left side of Pluto’s “heart” and is completely impact-free in all images returned to date.
Scientists wondered whether Sputnik Planum’s smooth, icy plains were an oddity. Did a recent geological episode form the plains long after all other geologic activity ceased?
Apparently not. Crater counts reveal the presence of intermediate or “middle-aged” terrains on Pluto as well, suggesting that Sputnik Planum is not an anomaly—that Pluto has been geologically active throughout much of its more than 4-billion-year history. “We’ve mapped more than a thousand craters, which vary greatly in size and appearance,” said postdoctoral researcher Kelsi Singer, of the Southwest Research Institute in Boulder, Colo. “Among other things, I expect cratering studies like these to give us important new insights into how this part of the solar system formed.”
Building Blocks of the Solar System
Crater counts are giving the New Horizons team insight into the structure of the Kuiper Belt itself. The dearth of smaller craters across Pluto and its large moon Charon indicates that the Kuiper Belt likely had fewer smaller objects than some models had predicted. This leads New Horizons scientists to doubt a long-standing model that all Kuiper Belt objects formed by accumulating much smaller objects of less than a mile wide. The absence of small craters on Pluto and Charon supports other models theorizing that Kuiper Belt objects tens of miles across may have formed directly, at their current—or close to current—sizes.
In fact, the evidence that many Kuiper Belt objects could have been “born large” has scientists excited about New Horizons’ next potential target—the 30-mile-wide (40- to 50-kilometer-wide) Kuiper Belt object named 2014 MU69—which may offer the first detailed look at just such a pristine, ancient building block of the solar system.
And About Those Moons!
The New Horizons mission is also shedding new light on Pluto’s collection of moons and their unusual properties. For example, nearly every other moon in the solar system, including Earth’s moon, is in synchronous rotation, but not so for Pluto’s small moons. These small satellites are spinning much faster, with Hydra—the most distant moon—rotating an unprecedented 89 times during a single lap around Pluto. Scientists believe these spin rates could be chaotic (i.e., variable) because Charon exerts a strong torque that prevents each small moon from settling down into synchronous rotation, which means keeping one face toward the planet.
Another oddity of Pluto’s moons: scientists expected the satellites to wobble, but not to this degree. “Pluto’s moons are behaving like spinning tops,” said Co-investigator Mark Showalter of the SETI Institute in Mountain View, Calif.
Images of Pluto’s four smallest satellites also indicate that several of them could have been born from mergers of two or more former moons, suggesting the presence of more moons at some point. “We suspect from this that Pluto had more moons in the past, in the aftermath of the big impact that also created Charon,” said Showalter.
Onward to 2014 MU69
On Nov. 4, 2015, the New Horizons engineering team completed the last of four targeting maneuvers that set New Horizons on course for a January 2019 encounter with 2014 MU69. This ancient body in the Kuiper Belt is more than a billion miles beyond Pluto; New Horizons will explore it if NASA approves an extended mission.
The four propulsive maneuvers were the most distant trajectory corrections ever performed by any spacecraft. Safely programmed into New Horizons’ onboard computers, the fourth maneuver executed at approximately 1:15 p.m. on Wednesday, Nov. 4, and lasted just under 20 minutes. Spacecraft operators at APL confirmed data through NASA’s Deep Space Network to indicate the final targeting maneuver proceeded as planned.Back to top
Closest Approach Celebration
APL’s Kossiakoff Center was New Horizons mission central for the week of July 12–18. Nearly 250 members of the media, 1,600 guests, and hundreds of APL staff members converged there for panel discussions, press conferences, and related activities, as close as a Plutophile can get to the mission operations and science activities. A full NASA TV set was built on the center’s auditorium floor for the panels and talks, and for the flyby coverage that was broadcast and webcast to the world.
New Horizons was actually out of contact with Earth during its closest approach to Pluto at approximately 7:50 a.m. EDT on July 14, but team members, along with over 1,000 Kossiakoff Center guests and a TV audience, marked the flyby with a raucous countdown, led by mission Principal Investigator Alan Stern and APL Director Ralph Semmel. Live media coverage of the event showed many U.S. flags waving and cheers and hugs around the room when the countdown was complete.
Later that morning, the team revealed a stunning, immediately iconic image of Pluto, the last photo New Horizons took and transmitted before resuming science operations and entering flyby silence.
Few can dispute Pluto’s popularity. The Pluto flyby by New Horizons was one of NASA’s most successful media operations to date, with more than 14,000 media reports from July 14–20, and Pluto images graced the front page of nearly 450 newspapers worldwide on July 14. On social media, the initial image was released to Instagram by NASA and quickly garnered 350,000 likes. NASA and New Horizons tweets and replies made 70 million impressions on Twitter, and New Horizons/Pluto posts reached 144 million Facebook users. In the hour before the Pluto flyby, 42 percent of all traffic on government websites was at nasa.gov. Nearly 1 million visitors came to the mission’s webpage: http://pluto.jhuapl.edu/.Back to top
Sector Head's Note
From New Horizons to MESSENGER and Onward to the Sun
In my 2 years as sector head, it has been a privilege to witness many of the technical accomplishments that APL has to offer. The technical breadth of work done within the Space Exploration Sector is broad, and it still continues to astonish me.
This past July, we were delighted and amazed by the first images from Pluto. However, the road to success is not always simple; 10 days before the planned encounter, the spacecraft went into safe mode, and at APL, cell phones started ringing so that the team could reassemble and begin recovery operations. With less than 10 days before encounter, any issues needed to be understood, resolved, and closed in very short order to ensure that the entire mission objective was successful. With many coffee pots and cots put to good use, the root cause was determined, a resolution was tested, and the result was successfully uploaded.
For me, witnessing the teamwork that was required to resolve this problem was fascinating: the teamwork, communication, and leadership were impeccable. Some dogged engineering skills were required to complete the root cause analysis in time, but the team worked on it hard and never lost sight of the goal. Our mission ops manager, Alice Bowman, slept in her office for several days and yet still managed to look dynamic and like the thoughtful leader she is during the encounter broadcasts. The worldwide audience for the encounter was a new experience for the Laboratory, but the benefit of public engagement and interaction seemed to energize both APL and JHU campus wide. This newsletter covers some of the elements of the long and thrilling days of Pluto flyby.
As 2016 approaches, we look forward to the Juno mission arriving at Jupiter with an APL-built particle detector, as well as more developments from the New Horizons download of data from the Pluto system, which continues for most of 2016 due to low data rates at that distance from Earth. As Solar Probe Plus (SPP) ramps up into full integration and test later in 2016, our facilities will be humming with activity. More details on SPP activity and science objectives will be provided in future newsletters.
I have enjoyed making the rounds at conferences and events to get to know many of our sponsors and partners. If for some reason, you want to reach me, but can’t, please see the contact information listed on the back of this newsletter.
Space Exploration Sector Head
Milestones and More
NASA’s STEREO-A Resumes Normal Operations
On Nov. 9, 2015, NASA’s Solar and Terrestrial Relations Observatory Ahead, or STEREO-A, resumed transmitting data at its full rate. For the previous year, STEREO-A had been transmitting only a weak signal—or occasionally none at all—due to its position almost directly behind the Sun, known as conjunction. By Nov. 17, STEREO resumed its normal science operations, which includes transmission of lower-resolution real-time data—used by scientists to monitor solar events—as well as high-definition, but delayed, images of the Sun’s surface and atmosphere.
STEREO is sponsored by NASA Headquarters’ Science Mission Directorate, Washington, D.C. NASA Goddard Space Flight Center’s Solar Terrestrial Probes Program Office, in Greenbelt, Md., manages the mission, instruments, and science center. APL designed and built the spacecraft and operates the observatory for NASA during the mission.
Van Allen Probes Celebrate Third Anniversary of Launch and Extended Mission
On Aug. 30, 2015, 3 years after the Van Allen Probes were launched from the Cape Canaveral Air Force Station in Florida, the twin spacecraft continue to push the boundaries of what is known about the space above our world. The probes collect data on the two radiation belts that surround Earth and have revealed intriguing new details on the Sun’s influence on our planet.
The spacecraft—built and operated by APL—are flying in nearly identical eccentric orbits, which span Earth’s entire radiation belt region. The mission recently received the highest rating for scientific achievement in the NASA Heliophysics Division Senior Review of operating missions, and it was granted approval for a 2-year extension. Van Allen is the second mission in NASA’s Living With a Star program and provides scientists the opportunity to extend their study of radiation belts’ energization, loss, and transport processes into a period when solar activity is diminishing.
“We’re moving into the declining phase of the solar cycle, which is often when the biggest geomagnetic storms occur,” said Project Scientist Sasha Ukhorskiy. “The Van Allen Probes extended mission will help us understand how radiation belts evolve during extreme space-weather events.”
Mission extension is possible, in part, because of the resilience of these tough, well-protected probes, which were built to survive the harsh radiation environment of the belts. “The spacecraft are both in really great shape,” said Mission Engineer Kristin Fretz. “The science and engineering teams have been working closely together to optimize the probes’ flight and provide more lapping events. At the same time, we figured out a way to eliminate north–south maneuvers that were scheduled approximately every 6 months; the elimination of these maneuvers saves propellant and extends the life of the mission by 1 or 2 months per maneuver.”
NASA Administrator Charles Bolden and Brazilian Space Agency President Jose Raimundo Braga Coelho recently signed agreements that will allow Brazil to access data from the Van Allen Probes mission, furthering the mission’s science objectives and increasing the quantity of space-weather data that can be made available. Read more about the Van Allen Probes’ space-weather data products here: http://vanallenprobes.jhuapl.edu/newscenter/newsArticles/20140829.php.
On April 30, 2015, APL mission controllers confirmed that NASA’s MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft impacted the surface of Mercury, as predicted, at 3:26 p.m. EDT. With no propellant remaining to increase its altitude, MESSENGER was fated to impact the surface of Mercury at some point, and it slammed into the planet at around 8,750 miles per hour, creating a new crater up to 52 feet wide.
MESSENGER was launched on Aug. 3, 2004, and it began orbiting Mercury on March 18, 2011. The spacecraft completed its primary science objectives by March 2012. Because MESSENGER’s initial discoveries raised important new questions and the payload remained healthy, the mission was extended twice, allowing the spacecraft to make observations from extraordinarily low altitudes and capture images and information about the planet in unprecedented detail.
During the short extension of the MESSENGER mission referred to as XM2, the spacecraft was running on fumes of propellant. The team embarked on a hover campaign that allowed the spacecraft at its closest approach to operate within a narrow band of altitudes, 5–35 kilometers above the planet’s surface. On April 28, the team successfully executed the last of seven orbit-correction maneuvers (the last four of which were conducted entirely with helium pressurant after the remaining liquid hydrazine had been depleted), which kept MESSENGER aloft for the additional month, sufficiently long for the spacecraft’s instruments to collect critical information that could shed light on Mercury’s crustal magnetic anomalies and ice-filled polar craters, among other features.
TIMED Celebrates 5,000 Days of Data Collection, Sixth Extended Mission
The NASA TIMED (Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics) spacecraft, which studies the impact of solar- and human-induced disturbances on Earth’s upper atmosphere, celebrated 5,000 days of continuous data collection on Aug. 15, 2015. During the past 14 years, the spacecraft has completed more than 74,000 Earth orbits and accumulated more than 9 terabytes of data, served by the TIMED Mission Science Data Center located at APL and now archived at the Space Physics Data Facility at the NASA Goddard Space Flight Center.
The TIMED spacecraft—built and operated for NASA by APL in Laurel, Md.—was launched in December 2001. The mission recently received high grades in the 2015 NASA Heliophysics Division Senior Review and was approved for a sixth extended mission.Back to top
APL’s Denevi Earns Top Scientist from Maryland Academy of Sciences
The Maryland Academy of Sciences named MESSENGER scientist and APL staff member Brett Denevi Outstanding Young Scientist during a ceremony on Nov. 18 at the Maryland Science Center in Baltimore.
The Outstanding Young Scientist award program was established in 1959 to recognize and celebrate extraordinary contributions of young Maryland scientists. During her postdoctoral studies at Arizona State University and later as a planetary geologist in APL’s Space Exploration Sector, Denevi was instrumental in helping to answer critical science questions posed by the MESSENGER mission to Mercury. She led research that showed Mercury has a volcanic crust, and she developed maps of different geologic units that were used by the MESSENGER science team to address questions about Mercury’s composition and the evolution of its interior.
While doing this research, she also planned MESSENGER observations of the innermost planet and led the effort to calibrate the images the Mercury-orbiting spacecraft sent back to Earth. Denevi holds key roles on two other active planetary missions as well, as a co-investigator on the Lunar Reconnaissance Orbiter Camera and a participating scientist on the Dawn asteroid-study mission.
In addition to her career in geophysics, Brett is an accomplished ballerina and has been featured in the Washington Post as an accomplished scientist with a passion for dance. Her love of ballet explains some of the more graceful crater names on Mercury, such as Balanchine and Fonteyn.
To learn more about Denevi’s work, visit: https://www.youtube.com/watch?v=oYQSf2aMaTg&feature=youtu.be.Back to top
APL Investigators, Instruments Selected for Future NASA Planetary Mission Studies
Five Space Exploration Sector researchers from APL in Laurel, Md., will serve as co-investigators on proposals for NASA’s next Discovery Program mission. Additionally, two APL-built instruments—based on heritage instruments flown aboard APL-built NASA missions—were also among the five proposals selected by NASA for further study on Sept. 30, 2015.
The Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) mission would study the chemical composition of Venus’ atmosphere during a 63-minute descent. It would answer scientific questions that have been considered high priorities for many years, such as whether there are volcanoes active today on the surface of Venus and how the surface interacts with the atmosphere of the planet.
As a DAVINCI co-investigator, APL’s Ralph Lorenz would lead the Venus Atmospheric Structure Investigation (VASI), which would use accelerometers and pressure and temperature sensors to characterize the Venus atmosphere profile at altitudes that have not been measured well by previous probe missions. Data from these sensors will help set the context for the chemistry measurements to be made by DAVINCI and will help refine estimates of its landing location. Lori Glaze of NASA’s Goddard Space Flight Center in Greenbelt, Md., is the DAVINCI principal investigator.
Noam Izenberg of APL is also a DAVINCI co-investigator; he would use data from the spacecraft to study the surface and atmosphere interface. In particular, his work would focus on the carbon and oxygen balance and equilibrium, which would reveal information about the mineralogy of Venus’ surface. Additionally, Izenberg would lead a student collaboration experiment (if selected) that would examine specific characteristics of the oxygen in the atmosphere. The experiment would be primarily designed and built by students at the Johns Hopkins University in Baltimore.
David Lawrence and Patrick Peplowski of APL are co-investigators on the Psyche mission proposal, which would explore the origin of planetary cores by studying the metallic asteroid 16 Psyche, which is composed most likely of iron/nickel metal. Lawrence is the lead co-investigator in charge of the APL-built Gamma-Ray and Neutron Spectrometer (GRNS), and Peplowski would serve as the GRNS instrument scientist. The GRNS, which is based on a similar instrument built by APL for the MESSENGER spacecraft, will be built in collaboration with Lawrence Livermore National Laboratory. The GRNS and other instruments on the Psyche spacecraft will characterize the composition and geology of 16 Psyche in order to understand the development of planetary metallic cores. Linda Elkins-Tanton of Arizona State University in Tempe, Ariz., is the Psyche principal investigator.
The Lucy Long Range Reconnaissance Imager (L’LORRI) builds on the success of the APL-built LORRI camera currently on board the New Horizons Pluto-Kuiper Belt mission. The camera would fly aboard a spacecraft called Lucy that would perform the first reconnaissance of the Jupiter Trojan asteroids, objects thought to hold vital clues to deciphering the history of the solar system. Hal Weaver of APL is the L’LORRI instrument lead; Harold Levison of the Southwest Research Institute in Boulder, Colo., is the Lucy mission principal investigator.
NASA selected five science investigations for refinement during the next year as a first step in choosing one or two missions for flight opportunities as early as 2020. After a detailed review and evaluation of the concept studies, NASA will make the final selections by September 2016 for continued development leading up to launch.
In addition to leading the MESSENGER mission, APL led the first Discovery-class mission, NEAR, which in 2000–2001 became the first spacecraft to orbit and land on an asteroid, Eros. Created in 1992, the Discovery Program sponsors frequent, cost-capped solar system exploration missions with highly focused scientific goals. The program has funded and developed 12 missions to date.
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