Saturn’s rings may be more massive than previously thought. Both Cassini observations and theoretical simulations of Saturn’s rings point towards extensive particle clumping in Saturn’s rings. Our simulations of the rings show that the surface density of particles can be substantially larger than one would infer from a uniform distribution of particles. The gravitational attraction between ring particles causes the particles to bunch up into clusters that organize themselves into connected strands resembling a giant spider web. As the particles orbit Saturn, strands of the spider web are slowly sheared apart and new strands are formed. Adding more particles to the simulation simply piles more particles onto the spider web strands while leaving relatively clear gaps in between the strands of the spider web.

As a result, when the Cassini spacecraft observes the light of a star passing through the densest part of the rings, it is actually measuring the fractional area between these opaque strands of particles rather than the density of material within the spider web itself. When we calculate the amount of light that can pass through our simulation of the rings, we see strong variations with the viewing geometry similar to the variations observed by the Cassini Ultraviolet Imaging Spectrometer (UVIS) instrument when starlight passes through the rings.

We estimate that the densest part of the Saturn’s ring, located in the core of the B ring, contains more than three times the mass previously estimated. The inferred total mass of Saturn’s ring is therefore likely to be at least three times more massive than the satellite, Mimas. Such a massive ring system is unlikely to have formed by the tidal disruption of a comet or by the collisional disruption of a former satellite during the last 4 billion years. Instead, we argue that the massive B ring must have a primordial origin, dating back from the period of late heavy bombardment when the collisional disruption of a massive satellite was more probable. Placing a massive satellite inside Saturn’s Roche zone by orbital migration due to resonant interactions with a proto-satellite disk may even be a natural outcome in the context of Canup and Ward’s model of satellite formation in a “gas-starved” accretion disk around Saturn.

So how do we reconcile this scenario with youthful features in Saturn’s rings? The massive B ring could be quite ancient while the A and C rings are still relatively young. Our simulations suggest that the spreading rate of the B ring is substantially slower than in the A ring because the extensive particle clumping in the B ring results in a slow taffy pull of long strings of particles rather than the vigorous stirring seen in the A ring simulations. In this scenario, the massive B ring evolves slowly while the lower mass A ring and C ring evolve faster and show the most evidence for youthful features.

Through the early history of the Upper Air Laboratory, Fred made significant contributions to the stability of the program, securing funding from NRL and AFGL. Fred served as the Director of Operations for what ultimately became the Laboratory for Atmospheric and Space Physics for more than two decades. He directed much of the technical efforts for LASP’s early space missions, including OSO, OGO, and the Mariner missions, as well as the engineering efforts for more than 150 sounding rockets and balloon payloads. He was the principal engineer in the development of the Bi-axial pointing systems developed by LASP (in conjunction with NRL and AFGL) in the late 1950′s and 1960′s, the first reliable pointing system ever developed. He was a primary contributor to the technologies that led to LASP’s first EUV and XRay measurements of the sun. Fred participated in the development of the original SPARCS systems (Solar Pointing Aerobee Rocket Control System) in the early 1960′s. These systems were used to point and control the entire rocket payload, once separated from the motor, as opposed to just pointing the instrument. The SPARCS system has been and continues to be the workhorse for NASA’s solar pointed sounding rocket missions to this day.

Fred retired from LASP in 1987. He continued to support the University of Colorado’s students programs, including CSOAR and the Student Nitric Oxide Explorer through the mid-1990′s.

Fred’s service will be at 11:00 a.m. on Saturday 5/19/07 at the Estes Valley Memorial Gardens 1672 Fish Hatchery Road, Estes Park, CO 80517.

Memories

I remember Fred as a gentle and friendly man, always willing to help and talk through issues. He was certainly one of the persons who helped to build LASP’s good reputation in the early days. Thanks, Fred.

— Dave Rusch, May 18, 12:06 PM

When I first started at LASP in 1965 I was working with the rocket group producing the rocket log book plots of rocket and instrument performance from the analog strip charts made at launch. Fred had a bowling ball and plastic protractor by which we determined where the instrument was pointing during the flight. When I came down with the flu one summer, they brought that bowling ball over to Wardenberg Hospital so I could calculate the pointing from my hospital bed. The last time I asked, Fred still had that bowling ball! We laughed and laughed over that ball. But it worked; Fred had a way of making things work, and always smiling about it too. He made a difference in my life. I’ll miss him.

— Karen Simmons, May 18, 01:42 PM

Fred was there in the beginning of research rockets for CU in the late 1940s, and he was also there for the latest LASP rocket. Fred and his family were able to visit White Sands Missile Range (WSMR) during our rocket integration and launch last October for NASA 36.233 (TIMED SEE calibration rocket). He logged a many hours at White Sands along with many fine adventures there.

Fred contributed so much to LASP, the national rocket program, and NASA in general. We are all so proud of what he has accomplished and done for our laboratory. Thanks Fred!

— Tom Woods, May 18, 02:32 PM

Perhaps because it housed the lab coffee pot, the social center of the old LASP engineering building on 55th Street in Boulder was the instrument shop. Fred came through the shop (and visited the coffee pot) every morning on the way to his office. He did not simply walk into the shop; he always made an entrance, pausing just inside the doorway to sing out a brief, cheery yodel. It was a moment of morning cheer for everyone within earshot, and I miss it.

— Mark Lankton, May 18, 03:36 PM

When I first started designing systems to control mirrors and point them at things, stars and planets, I started from scratch. Fred’s notebooks, dating back to his days with the development of the biaxial pointing system, and Fred’s mentoring were invaluable resources that helped teach me the things I needed to learn.

In general I learned so much about the engineering we do from long discussions with Fred.

Thanks Fred, I have always and will always appreciate all of your help.

— Jim Westfall, May 18, 07:33 PM

Fred was smart, funny, tough, and very proud. He was an engineer’s engineer. I’ve never before or since seen a more versatile, seat of the pants engineer. I learned a great deal from Fred, as did many, many others.

Thanks Fred, you taught so many what it means to be a fine engineer.

— Alan Stern, May 19, 08:03 AM

I went with Fred to Fort Churchill in 1969. It was the worst Airplane flight of my life with too many bumps. Fred taught me how to be brave -focus on the rocket shot for science and drink scotch.

— Joe Ajello, May 30, 08:15 PM

Rest in peace, Fred.

The team, led by CU-Boulder’s Laboratory for Atmospheric and Space Physics, will receive $2 million from NASA for a nine-month “Phase A” study for the proposed Mars Atmosphere and Volatile Evolution mission, or MAVEN.

MAVEN was proposed as part of NASA’s Scout Program, which has a cost cap of $475 million. The second proposal selected for further study is led by the Boulder office of the Southwest Research Institute, headquartered in San Antonio. The winning proposal is expected to be selected for flight in about one year.

The CU-Boulder proposal includes a spacecraft with 10 instruments that will focus on the upper atmosphere of Mars, said LASP Associate Director Bruce Jakosky, principal investigator for MAVEN. LASP would have overall responsibility for the mission, including providing two instruments and half of a third instrument. LASP also would provide science operations for the mission and managing the education and outreach program, he said.

Partners on the LASP proposal include NASA’s Goddard Space Flight Center in Greenbelt, Md., Lockheed Martin Corp. of Denver, the University of California, Berkeley, and the University of Michigan. Lockheed Martin would provide the spacecraft, as well as mission operations, for the MAVEN mission.

“We think we have proposed a first-rate mission with outstanding science and outstanding partners, and are extremely excited about the NASA announcement,” said Jakosky, an internationally known Mars expert. “Scientists have a lot of questions about the loss of water and carbon dioxide from the Martian atmosphere over time, which have implications for the possibility of past or present life there.”

LASP Director Daniel Baker, one of the science team members on MAVEN, described it as “a telescope-microscope mission that will allow scientists to piece together an entire picture of the Martian atmosphere. We want to better understand how the Mars atmosphere evolved, its present state, and what we might see happening there in the future,” he said.

The MAVEN science team includes three LASP scientists heading instrument teams — Nicholas Schneider, Frank Eparvier and Robert Ergun — as well as a large supporting team of scientists, engineers and mission operations specialists.

If selected for flight, MAVEN would include participation by a number of CU-Boulder graduate and undergraduate students in the coming years, said LASP faculty member Fran Bagenal, a member of the MAVEN science team. Currently there are more than 100 undergraduate and graduate students working on research projects at LASP, providing training for future careers as engineers and scientists, she said.

The MAVEN effort also would bring together undergraduate data teams from across the nation to help analyze mission results, Baker said.

Multiple lines of evidence suggest that Mars lost most of its atmosphere several billion years ago, said Jakosky. The MAVEN orbiter would study current atmospheric loss with emphasis on the role of the solar wind, including its rapidly moving charged particles and magnetic field that may be responsible in large part for the current atmospheric conditions on the Red Planet, he said.

NASA’s Mars Exploration Program was designed to help characterize and understand Mars as a dynamic system, including its present and past environment, climate cycles, geology and biological potential. The Mars Exploration Program is managed by NASA’s Jet Propulsion Laboratory in Pasadena, Calif.