Philosophical Society of Washington

Minutes of the 2380th Meeting

At the Cosmos Club, Washington, DC
October 6, 2017

President Larry Millstein called the 2,380th meeting of the Society to order at 8:05 p.m. Being the first meeting of the year, this was the annual meeting of the Society.  President Millstein summarized the annual reports of the officers and the Society’s good health. He then welcomed new members. The minutes of the previous meeting were read and approved. President Millstein then introduced the speaker for the evening, James B. Garvin, Chief Scientist, NASA Goddard Space Flight Center. His lecture was titled “Searching for Signs of Habitability and Life on Other Ocean Worlds.”

Dr. Garvin began by noting the 30th anniversary of NASA’s Voyager mission to the edge of our solar system. He then moved to discussing a nearby ocean world bigger than our own.

Europa, the Jovian moon first examined by the Voyager spacecraft, has a land area approximately the size of Africa. Scientists believe this moon has an ocean that is volumetrically the size of our own here on Earth. Also like Earth, we have reason to believe this “cueball planet” is a dynamic world, with a crust that deforms 100 feet per orbit, due to its ocean.

Unlike Earth, Europa lies in the radiation belts of Jupiter, which is not conducive to long-chain organic molecules that all humans are made of. Garvin said the best working hypothesis for life on Europa is a large, 100-kilometer-deep ocean, covered by a crust of silicate ice several miles deep, shielding ocean life from radiation. This hypothesis is supported by reconnaissance from the Voyager and Galileo spacecraft.

To be sure whether there is life on Europa, according to Garvin, we must go there. Garvin likened the vision for going to Europa to NASA’s exploration of Mars. NASA sent the Viking spacecraft to Mars in 1976, to read the chemistry of the environment. NASA subsequently sent a gas-chromatograph mass spectrometer, landing a lab on Mars in 2012. In the years since landing on Mars, NASA has discovered organics, a methane cycle, and chlorobenzenes – but not the life signs scientists were hoping for. For Mars, “the fun stuff” is all in the past.

Ocean worlds, however, present better prospects for finding life that is still present. Europa is home to the most accessible foreign ocean in the Solar System, with liquid close to the surface and potential fissures in its ice crust. “The exciting stuff,” Garvin said, would be seeping or bursting through Europa’s crust. But, it has a short resonance time because of Europa’s intense surface radiation.

Today, NASA can land on Mars within 10 kilometers of the target, which Garvin calls exceptional. But the good stuff on Europa may be located within an area of only a kilometer. If NASA is going to land a static lab on Europa to conduct in situ analysis, NASA needs to improve its landing accuracy. So, Garvin proposes to leverage the James Webb Space Telescope’s spectral power to examine the chemistries of small surface areas to identify potentially fruitful surface areas. Then, the CLIPPER mission will follow, in the early 2020s, for habitability reconnaissance.

CLIPPER will provide the requisite resolution to understand Europa’s terrain and paint a picture of the surface in sufficient detail to accurately land a laboratory.

After figuring out where to land, Garvin thinks a landing mission to Europa in the early 2030s would be possible. To make that mission a reality, NASA will need to balance the quantity and quality of the answers it wants, with the cost of obtaining them. The intense radiation on the surface of Europa limits the lifespan of any instrument, and mobility increases the cost.

The current plan for a Europa lander is a static lander. Because the lander will not be able to move, it will have cricket-like stabilizers, rather than firm legs. As such, the lander is affectionately called, “The Cricket.” The Cricket’s body is a vault, protecting its sensitive instruments, capable of processing up to five samples to answer a series of research questions.

Garvin expects that analyzing the first data from the first lander will lead to additional research questions and inspire future missions. Already, there is discussion of sending a walking rover, a sample return mission, and missions using soft robots.

Garvin views the Europa mission as the first of many ocean world explorations. Potential future missions could take us to Saturn’s moon Enceladus, or even to Pluto.

Garvin concluded by saying that exploring for life in our own solar system will teach us how to look for life in other star systems.  NASA is beginning to develop tools for this that can detect spectral signatures suggesting atmospheres capable of supporting life on worlds around other stars.

President Millstein then invited questions from the audience.

One questioner asked where is the best place to land Europa.  Garvin responded that a prime target would be around a fresh vent spewing organics.

Another questioner asked why the Europa lander was not nuclear-powered, possibly saving money. Garvin responded that the expected life time in that environment is too short to justify the additional weight for nuclear power.

After the question and answer period, President Millstein thanked the speaker, made the usual housekeeping announcements, and invited guests to join the Society. At 9:47 p.m., President Millstein adjourned the 2,380th meeting of the Society to the social hour.

Attendance: 106
The weather: Light rain
The temperature: 25°C

Respectfully submitted,

James Heelan
Recording Secretary

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