The National Polar-orbiting Operational Environmental Satellite System (NPOESS) is an example of a space program that relies on inter-agency cooperation. A new NRC report defines this type of collaboration as the most high-risk. LASP was building the Total Solar Irradiance Sensor, or TSIS, for the program. Since the NPOESS restructuring earlier this year, the NASA/NOAA Joint Polar Satellite System (JPSS) has taken over management of TSIS, which is now a free-flyer mission. (Artist’s rendition courtesy NOAA)

A new National Research Council report, co-chaired by Daniel Baker of CU/LASP and D. James Baker of the William J. Clinton Foundation, concludes that cooperation among federal agencies on space programs leads to costlier programs with greater risk and complexity.

Daniel Baker said, “In many cases, an individual agency would do well to consider alternatives to full partnerships and instead buy specific services or coordinate spaceflight data from other agencies. However, if full collaboration is deemed to be warranted, then the agencies must take special care to ensure that disciplined attention to systems engineering and best practices for project management are followed.”

The report also concurs with a previous Research Council report that recommends action by an executive branch entity above the agency-level to correct mismatches of authority and responsibility, inconsistent mandates, and budgets that are not well suited for emerging needs.

The report, Assessment of Impediments to Interagency Collaboration on Space and Earth Science Missions, was led by a committee that examined case studies from previous domestic and international missions, received briefings from several agencies, and drew upon committee members’ own experiences to reach its conclusions.

The National Research Council is the principal operating agency of the National Academy of Sciences and the National Academy of Engineering. NASA sponsored the study.

The newly announced Sun-Climate Research Center, a collaboration between LASP and Goddard, will focus on research areas such as how solar variations shape Earth’s atmosphere and climate. This image of the sun is from the LASP-built NSF Precision Solar Photometric Telescope (PSPT). (Courtesy NASA/GSFC Scientific Visualization Studio; source data courtesy of HAO and LASP PSPT project team)

The University of Colorado Laboratory for Atmospheric and Space Physics (LASP) and NASA’s Goddard Space Flight Center announced the formation of a new collaborative research center dedicated to the study of the Sun’s effect on Earth’s climate. The center, called the Sun-Climate Research Center (SCRC), will be directed by Peter Pilewskie, a LASP research scientist and CU professor, Robert Cahalan, Head of Goddard’s Climate and Radiation Branch, and Douglas Rabin, Head of Goddard’s Solar Physics Laboratory.

Pilewskie said, “The exciting thing about this collaboration is that we believe it will promote studies to help answer a key question about the climate system: how does Earth’s atmosphere respond to the sun’s variability, and how does that affect climate? This question is particularly important now, as we seek to quantify the human-induced impact on Earth’s climate.”

The SCRC, which has been made possible by a Federal Space Act Agreement, will foster collaboration between Earth-atmosphere and solar sciences at the two institutions. Opportunities will include a scientist exchange program between the organizations, the ability for post-doctoral scientists and graduate students in science, engineering, and mission operations to move between LASP and Goddard, annual international Sun-Climate research symposia, and the ability for the two institutions to collaborate more fluidly on future research opportunities.

Robert Cahalan, SCRC co-director and Goddard scientist, said, “In recent years Goddard and LASP have worked together on several Earth and Sun missions. Now we look forward to continuing to drive growth in this key interdisciplinary field of Sun-Earth research, bringing new focus to the study of multiyear changes in the Sun and their influence on Earth’s climate.”

With a limited number of such agreements between U.S. universities and any of NASA’s ten field centers, the SCRC represents a rare and innovative step, underscoring LASP’s ability to develop high-caliber research and programmatic opportunities with Goddard.

Daniel Baker, LASP Director, said, “LASP has developed some remarkable areas of expertise that are key to studying the sun and its effect on climate and on human activities. By working with our colleagues at Goddard, we can leverage our skills—and help take an important step toward greater cooperation between NASA centers and leading university research teams.”

Contacts:

LASP:
Peter Pilewskie, SCRC Director: 303-492-5724 or
Peter.Pilewskie@lasp.colorado.edu

Dan Baker, LASP Director: 303-492-4509 or
Daniel.Baker@lasp.colorado.edu

Stephanie Renfrow, press office: 303-735-5814 or
Stephanie.Renfrow@lasp.colorado.edu

Goddard Space Flight Center:
Robert Cahalan, SCRC Co-Director: 301-614-5390 or
Robert.F.Cahalan@nasa.gov

Scientists believe that ice caves may be found in the known lava tubes on Mars; such ice caves could harbor Martian life, and would be useful to future space explorers. (Courtesy NASA)

A recent study co-authored by LASP researcher Brian Toon used models to predict which regions on Mars could have ice caves. Ice caves are sometimes found on Earth in lava tubes left over from previous volcanic activity; on Mars, these ice caves could allow ice to exist in middle latitudes, where many lava tubes have been found.

Toon said, “Martian ice caves would be important for two reasons: first, as a water source and protective home for future space explorers, and second as a good place to look for the possibility of life on Mars.”

The study was published in the October issue of Icarus. For more information, please contact the LASP press office at 303.735.5814 or Stephanie.renfrow@lasp.colorado.edu.

Citation
Williams, K.E., Christopher P. McKay, O.B. Toon, and James W. Head. 2010. Do ice caves exist on Mars? Icarus, Vol 209, Oct 2010, Pages 358-368. doi:10.1016/j.icarus.2010.03.039

CU/LASP physics graduate student Andrew Poppe operates SDC and analyzes the data.

The Venetia Burney Student Dust Counter (SDC), a CU/LASP-built instrument aboard the NASA New Horizons mission to Pluto, just became the record-holder for the most distant functioning space dust detector ever in space.

On October 10, the SDC surpassed the previous record when it flew beyond 18 astronomical units—one unit is the distance between the sun and the Earth—or 1.67 billion miles, which is approaching the orbit of Uranus. The only other dedicated dust instruments to measure space dust beyond the orbit of Jupiter were aboard Pioneers 10 and 11 in the 1970s. Additionally, SDC is the first science instrument on a planetary mission to be designed, tested, and operated by students.

“The New Horizons mission is going to break a lot of records, but this early one is one of the sweetest,” said New Horizons Principal Investigator Alan Stern, of Southwest Research Institute, Boulder, Colorado. “We’re very proud to be collecting solar system dust data farther out than any mission ever has, and we’re even prouder to be carrying the first student-built and -operated science instrument ever sent on a planetary space mission.”

Andrew Poppe, a LASP graduate student in physics who operates SDC and analyzes the data, said, “It’s a once-in-a-lifetime experience to be part of the group of students who made this happen. We built a record-breaking, successful instrument that is taking scientific measurements to advance our understanding of the role of dust in our solar system.”

Poppe and several collaborators recently published the first results from SDC in Geophysical Research Letters. Poppe said, “The SDC measurements of dust inside 5 astronomical units agreed well with the earlier measurements made by the Galileo and Ulysses missions. We also reported the first-ever measurements of sub-micron-sized dust grains in the outer solar system by a dedicated dust instrument.”

Poppe is one of five students on the current SDC team, and one of 32 who have worked on the instrument since the project began in 2002. The original team of approximately 20 undergraduate and graduate students has evolved over time, with new students brought into the fold as the nearly 20-year New Horizons mission has proceeded from concept development through launch and into its ongoing flight phase.

SDC instrument Principal Investigator Mihaly Horanyi, a LASP researcher and CU professor, said, “The SDC was built and tested to the same NASA engineering standards as professionally built flight instruments, under the supervision of professionals. Students have filled roles from science and engineering to journalism and accounting; many of them have graduated and gone on to careers in the space industry. In addition to its significant contribution to science, SDC proved to be an excellent investment in the scientists and engineers of tomorrow.”

LASP manages the SDC instrument project and has a long tradition of involvement with student instruments, including the Solar Mesosphere Explorer and the Student Nitric Oxide Experiment. LASP recruits both undergraduates and graduates from CU to help with instrument design, construction, maintenance, programming, and operations. Funding for the SDC came primarily from the NASA New Horizons mission, through the Johns Hopkins University Applied Physics Laboratory, which manages New Horizons; and the Southwest Research Institute, home institution of Stern and the center of New Horizons instrument observation planning. LASP has also contributed funds to help pay students working on the SDC. In June 2006, the instrument was renamed for Venetia Burney, the English schoolgirl who, at age 11, offered the name “Pluto” for the newly discovered ninth planet in 1930.

Citation:

Andrew Poppe, David James, Brian Jacobsmeyer, and Mihály Horányi. 2010. First results from the Venetia Burney Student Dust Counter on the New Horizons mission. Geophysical Research Letters, Vol. 37, L11101, 5 PP. doi:10.1029/2010GL043300

Journalists requiring more information, please contact Stephanie Renfrow, media relations, at 303-735-5814.

The LASP-led Mars Atmosphere and Volatile Evolution (MAVEN) mission launches in November 2013. (Courtesy NASA/JPL)

NASA announced today that the CU/LASP-led mission to Mars to investigate how the planet lost much of its atmosphere eons ago has been approved by the space agency to move into the development stage.

The effort, known as the Mars Atmosphere and Volatile Evolution, or MAVEN, mission, will explore the past climate of Mars, including its potential for harboring life over the ages. LASP is leading the mission, which will carry three instrument suites to probe the atmosphere of Mars and its interactions with the sun. LASP Associate Director and CU professor Bruce Jakosky is principal investigator on the mission.

Jakosky said, “A better understanding of the upper atmosphere and the loss of volatile compounds like carbon dioxide, nitrogen dioxide and water to space is required to plug a major hole in our understanding of Mars. We’re really excited about having the opportunity to address these fundamental science questions.”

The LASP team also will provide science operations, build two of the science instruments and lead education and public outreach efforts for the MAVEN mission.

Clues on the Martian surface, including features resembling dry riverbeds and minerals that only form in the presence of water, suggest Mars once had a denser atmosphere that supported the presence of liquid water on the surface. Since most of the atmosphere was lost as part of a dramatic climate change, MAVEN will make definitive scientific measurement of present-day atmospheric loss that will offer insight into the Red Planet’s history.

Michael Luther, on behalf of Ed Weiler of the NASA Headquarters Science Mission Directorate, led a confirmation review panel that approved the detailed plan, instrument suite and budget for the mission.

MAVEN Project Manager David Mitchell, of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said, “The team has successfully met every major milestone since selection two years ago. Looking forward, we are well positioned for the next push to critical design review in July 2011. In three short years we will be heading to Mars.” Launch is scheduled for November of 2013.

The three instrument suites on MAVEN will include a remote sensing package built by LASP that will determine global characteristics of the upper atmosphere. The MAVEN science team includes three LASP scientists heading up instrument teams—Nick Schneider, Frank Eparvier, and Robert Ergun—as well as a large supporting team of scientists, engineers and missions operations specialists.

The MAVEN effort also will include participation by a number of CU graduate and undergraduate students in the coming years, said Jakosky. Currently there are more than 100 students working on research projects at LASP, which provides training for future careers as engineers and scientists.

The confirmation review announced today authorized continuation of the project and set its cost and schedule. The next major mission milestone, the critical design review, will examine the detailed MAVEN system design. Assuming the critical design review is successful, the project team will assemble the spacecraft and its instruments.

The MAVEN contract is the largest ever awarded to CU-Boulder. NASA Goddard will manage the project, which will cost $438 million excluding the separately funded government-furnished launch vehicle and telecommunications relay package. Goddard also is building several science instruments for the mission.

Lockheed Martin of Littleton, Colorado, will build the spacecraft based on designs from NASA’s Mars Reconnaissance Orbiter and 2001 Mars Odyssey missions as well as perform mission operations. The University of California-Berkeley Space Sciences Laboratory also will build instruments for the mission and support education and public outreach efforts.

NASA’s Jet Propulsion Laboratory in Pasadena, California, will provide navigation support, the Deep Space Network, and the Electra telecommunications relay hardware and operations.

Journalists requiring more information, please contact Stephanie Renfrow, media relations, at 303-735-5814.

The set-up for launch of the instrument payloads took place in September under clear skies in Antarctica. (Courtesy Concordiasi team)

LASP atmospheric researchers Linnea Avallone and Lars Kalnajs are currently at McMurdo Station, Antarctica, where they are participating in the Concordiasi campaign, a French-led project to study the Antarctic “ozone hole” using instrumentation on long-duration, super-pressure balloons.

Two of the three balloons that are currently circumnavigating the lower stratosphere over Antarctica are carrying lightweight, low-power ozone photometers built in Avallone’s laboratory. Each instrument is making measurements of ozone every half-hour and is expected to continue for the lifetime of the payload—perhaps as long as four months. The data will be used in conjunction with simultaneous measurements of polar stratospheric clouds to learn more about the rates of ozone depletion and to constrain photochemical models.

Trajectories of Concordiasi balloons (as of 18 September 2100 UT) are shown over Antarctica. Click image to view full sized (Courtesy Cora Randall)

The NASA Solar Probe Plus spacecraft, which will carry instrumentation designed and tested at LASP, will orbit the sun to help scientists better forecast the radiation environment in which future space explorers will work and live.(Courtesy NASA)

A team of experts from LASP at CU-Boulder has been awarded $6.7 million from NASA to design, develop, and test instruments for the fastest space probe ever built. The probe will orbit 22 times closer to the sun than Earth, and well inside the orbit of Mercury, to better understand how the sun ticks.

Robert Ergun, LASP scientist and CU professor, is leading the LASP team that will design and test key components of the mission’s electrical and magnetic field instruments, including the spacecraft’s antennas and the onboard signal and data processing hardware. The LASP-CU effort is part of the Fields Experiment, which is led by the University of California, Berkeley; the package will measure electric and magnetic fields, radio emissions, and shock waves traveling through the sun’s atmospheric plasma.

Ergun said, “This has been more than 20 years in the making. It’s time for us to sharpen our pencils and refine our designs for what has finally become a real mission.” LASP Research Associate David Malaspina is a co-investigator on the effort.

The mission, a small-car-sized satellite known as Solar Probe Plus, is slated for launch in 2018. The probe will take five years to reach its closest orbit of the sun—zipping to within four million miles of it—in a region that has never been visited by a spacecraft. The satellite will be equipped with a high-tech heat shield to protect it from searing 2,550 degree Fahrenheit temperatures.

The mission should help scientists to better forecast the radiation environment in which future space explorers will work and live, according to NASA officials. At its closest point to the sun, the spacecraft will be traveling at 400,000 miles per hour—more than 100 miles per second.

Ergun said LASP is designing the “heart” of the Fields Experiment that will play a major role in the mission. “This is what we call forefront science—nobody has ever been this close to the sun before, and we hope it will eventually help us to understand how the universe works, since the sun is one of many trillions of stars in the universe and the only one that we can get to from Earth,” he said. ”As NASA puts it, this is our first visit to a star.”

The major question the Solar Probe Plus team hopes to answer is what drives the solar wind, a stream of charged particles whipping off the sun at millions of miles per hour that eventually affects the solar system and Earth, said Ergun. Another important question the scientists hope to answer is why the sun’s corona—a region of plasma surrounding the sun that is visible during solar eclipses—is hotter than its surface.

NASA is funding five proposals selected for Solar Probe Plus, including the Fields Experiment, for $180 million. The cost includes preliminary analysis, design development and tests. The four antennas that will be riding on the spacecraft as part of the Fields Experiment are each expected to be about 8 feet long and will be placed on each corner of the square heat shield and will be exposed to the sun, said Ergun.

Both the heat shield and the antennas will be made with a material known as “carbon-carbon,” which consists of a carbon fiber knitted together with a carbon matrix. “This will be one of the most challenging missions NASA has ever attempted,” Ergun said. “If the heat shield is even a few degrees off its angle toward the sun, the spacecraft will literally be toast.”

After launch, the spacecraft will make several flybys of Earth and Venus before setting out for orbit around the sun. The flybys will help to slow the spacecraft down and allow it to be inserted into the correct, elliptical orbit around the sun, said Ergun.

In addition to LASP-CU and the University of California, Berkeley, other participating institutions in the mission include the University of Minnesota, Goddard Space Flight Center in Greenbelt, Md., and the Paris Observatory.

For more information on the Solar Probe Plus mission visit http://solarprobe.gsfc.nasa.gov/. To view the NASA press release announcing the awarded investigations, visit http://www.nasa.gov/home/hqnews/2010/sep/HQ_10_208_Solar_Probe_Plus.html.

Contact:
Robert Ergun: 303-492-1560 or Robert.Ergun@colorado.edu
Stephanie Renfrow, LASP Communications: 303-735-5814
Jim Scott, CU-Boulder News Services: 303-492-3114

During the ICESat decommission, CU students worked seven days a week to supply NASA with information from the LASP Mission Operations Center. LASP is one of only a few university-based mission operations centers; LASP students perform mission operations for NASA satellites totaling more than $1.5 billion in value. (Courtesy LASP)

University of Colorado at Boulder (CU) Laboratory for Atmospheric and Space Physics (LASP) professionals and students have completed their role operating the NASA ICESat mission, one of five missions operated at LASP.  ICESat reached the end of its productive seven-year life in June, when NASA began decommissioning the satellite because of instrument failure. The remaining spacecraft debris fell to Earth in the Barents Sea at 5 a.m. EDT on Aug. 30.

Bill Possel, LASP Mission Operations and Data Systems Director, said, “CU undergraduates have controlled ICESat for the past seven years from our Mission Operations Center here at LASP. Although we are sad to see such a successful science mission come to an end, we are proud of our students’ role in bringing the spacecraft safely out of orbit.”

LASP is one of only a handful of institutes in the world that give undergraduates the training and certification to operate NASA spacecraft.  The opportunity to assist with decommissioning a spacecraft is even more rare. The last time a NASA science satellite re-entered Earth’s atmosphere was in January 2002, when the Extreme Ultraviolet Explorer re-entered the Earth’s atmosphere under conditions similar to ICESat. That satellite decommission was handled by NASA professionals.

ICESat debris landing area. Click map for high resolution. (Courtesy Google Maps)

Darren Osborne, LASP Flight Director for ICESat, said, “Our students had specific procedures to follow during the ICESat decommission. They ran calculations to determine where the spacecraft was located and made predictions for the NASA ground stations that tracked it. The students did this seven days a week until the decommission was complete.”

Using undergraduate students for spacecraft operations, although rare, offers a number of benefits. Possel said, “Student operators provide a lower cost to NASA, and CU students at LASP receive hands-on training and experience that helps position them for a future in space-related careers.”

ICESat has been important at CU not only because of the student role in operating the spacecraft, but because of the data that reside here. Data from ICESat’s Geoscience Laser Altimeter System (GLAS) instrument are archived at the National Snow and Ice Data Center (NSIDC) at CU. Although the mission is now over, NSIDC will continue to maintain the GLAS data archive and serve data and information to researchers who use the archived data in key research on elevation changes in Earth’s snow and ice. NSIDC is also the designated data archive for Operation IceBridge, a NASA airborne remote sensing mission that will fill the gap between the decommissioned ICESat mission and ICESat II, scheduled for launch in 2015.

The ICESat spacecraft was built by Ball Aerospace & Technologies Corp, also located in Boulder, Colorado.

More information

To learn more about the decommissioning of ICESat: http://icesat.gsfc.nasa.gov/icesat/index.php
To view NASA PR on ICESat re-entry: http://www.nasa.gov/mission_pages/icesat/icesat-end.html
To learn more about LASP Mission Operations: http://lasp.colorado.edu/home/mission-ops-data/
To learn more about students at LASP: http://lasp.colorado.edu/home/about/cu-students-at-lasp/
About the spacecraft: http://www.ballaerospace.com/page.jsp?page=188
To learn more about NSIDC’s role on ICESat: http://nsidc.org/monthlyhighlights/july2010.html

This artist’s concept illustrates the two Saturn-sized planets discovered by NASA’s Kepler mission. The star system is oriented edge-on, as seen by Kepler, such that both planets cross in front, or transit, their star, named Kepler-9. This is the first star system found to have multiple transiting planets. (Courtesy NASA/Ames/JPL-Caltech)

NASA announced today that the Kepler spacecraft, which is controlled by students and professionals in the LASP Mission Operations Center, has discovered the first confirmed planetary system with more than one planet transiting the same star.

The transit signatures of two distinct planets were seen in the data for the sun-like star designated Kepler-9. The planets were named Kepler-9b and 9c. The discovery incorporates seven months of observations of more than 156,000 stars as part of an ongoing search for Earth-sized planets outside our solar system. The findings will be published in Thursday’s issue of the journal Science.

Kepler is one of several missions currently operated at LASP; students take training to be certified operators with oversight from professionals.

For more information about LASP’s role on Kepler, please see http://lasp.colorado.edu/kepler-launch/missionoperations.html.

For more information on the discovery, read the NASA press release at http://www.nasa.gov/mission_pages/kepler/news/two_planet_orbit.html.

Fluctuations in Earth

LASP scientist and CU professor Tom Woods contributed to a study indicating that large changes in the sun’s energy output may drive unexpectedly dramatic fluctuations in Earth’s outer atmosphere. The study, published today in Geophysical Research Letters, links a recent, temporary shrinking of a high atmospheric layer with a sharp drop in the sun’s ultraviolet radiation levels.

The research, led by scientists at the National Center for Atmospheric Research and CU-LASP, indicates that the sun’s magnetic cycle, which produces differing numbers of sunspots over an approximately 11-year cycle, may vary more than previously thought.

“Our work demonstrates that the solar cycle not only varies on the typical 11-year time scale, but also can vary from one solar minimum to another,” said lead author Stanley Solomon, a scientist at NCAR’s High Altitude Observatory. “All solar minima are not equal.”

The findings may have implications for orbiting satellites, as well as for the International Space Station. The fact that the layer in the upper atmosphere known as the thermosphere is shrunken and less dense means that satellites can more easily maintain their orbits. But it also indicates that space debris and other objects that pose hazards may persist longer in the thermosphere.

“With lower thermospheric density, our satellites will have a longer life in orbit,” said CU-Boulder co-author Thomas Woods, a senior research associate at the Laboratory for Atmospheric and Space Physics. “This is good news for those satellites that are actually operating, but it is also bad because of the thousands of non-operating objects remaining in space that could potentially have collisions with our working satellites.”

The sun’s energy output declined to unusually low levels from 2007 to 2009, a particularly prolonged solar minimum during which there were virtually no sunspots or solar storms. During that same period of low solar activity, Earth’s thermosphere shrank more than at any time in the 43-year era of space exploration.
The thermosphere, which ranges in altitude from about 55 to more than 300 miles (90 to 500 kilometers), is a rarified layer of gas at the edge of space where the sun’s radiation first makes contact with Earth’s atmosphere. It typically cools and becomes less dense during low solar activity. But the magnitude of the density change during the recent solar minimum appeared to be about 30 percent greater than would have been expected by low solar activity.

The study team used computer modeling to analyze two possible factors implicated in the mystery of the shrinking thermosphere. They simulated both the impacts of solar output and the role of carbon dioxide, a potent greenhouse gas that, according to past estimates, is reducing the density of the outer atmosphere by about 2 percent to 5 percent per decade.

Their work built on several recent studies. Earlier this year, a team of scientists from the Naval Research Laboratory and George Mason University, measuring changes in satellite drag, estimated that the density of the thermosphere declined from 2007 to 2009 to about 30 percent less than during the previous solar minimum in 1996.

Other studies by scientists at the University of Southern California and CU-Boulder using measurements from suborbital rocket flights and space-based instruments, have estimated that levels of extreme-ultraviolet radiation—a class of photons with extremely short wavelengths—dropped about 15 percent during the same period.

However, scientists remained uncertain whether the decline in extreme-ultraviolet radiation would be sufficient to have such a dramatic impact on the thermosphere, even when combined with the effects of carbon dioxide.

To answer the question, Solomon and his colleagues turned to an NCAR computer tool, known as the Thermosphere-Ionosphere-Electrodynamics General Circulation Model. They used the model to simulate how the sun’s output during 1996 and 2008 would affect the temperature and density of the thermosphere. They also created two simulations of thermospheric conditions in 2008—one with a level that approximated actual carbon dioxide emissions and one with a fixed, lower level.

The results showed the thermosphere cooling in 2008 by 41 kelvins (about 74 degrees Fahrenheit) compared to 1996, with just 2 K attributable to the carbon dioxide increase. The results also showed the thermosphere’s density decreasing by 31 percent with just 3 percent attributable to carbon dioxide. The results closely approximated the 30 percent reduction in density indicated by measurements of satellite drag.

“It is now clear that the record low temperature and density were primarily caused by unusually low levels of solar radiation at the extreme-ultraviolet level,” Solomon said.

Woods said the research indicates that the sun could be going through a period of relatively low activity, similar to periods in the early 19th and 20th centuries. This could mean that solar output may remain at a low level for the near future.

“If it is indeed similar to certain patterns in the past, then we expect to have low solar cycles for the next 10 to 30 years,” Woods said.

The study was funded by NASA and by the National Science Foundation.