The Interstellar Age (13 page)

In any case, a group of people led by Jon Lomberg are awaiting expected approval by NASA to upload a yet-to-be-determined “digital interstellar message” into the
New Horizons
spacecraft’s permanent long-term flash memory once the mission has completed its science objectives. More than ten thousand people from
140 countries signed online petitions to support bringing this message project forward to NASA and the
New Horizons
project, which no doubt helped the idea gain official approval. The contents of the message—its text, images, art, and/or music—will be crowd-sourced, a distinctively more modern way of soliciting multiple opinions through the Internet. “Previous messages from Earth, portraits of our planet and our species, have been made by small groups of experts,” Jon Lomberg noted. “This initiative proposes that this time, for the first time, the whole world can participate. The
Voyager
record has become an iconic image of the twentieth century, signifying our emergence as a galactic species. Now, new generations can be captivated by the incredible perspective that creating a self-portrait of Earth offers, becoming better informed citizens of the galaxy in the process.”

I asked Jon to reflect on his motivation for taking advantage of the rare opportunity to once again include messages on an artifact being sent beyond our solar system. “Unfortunately, the
New Horizons
team was so busy just trying to keep their mission on track—it was canceled, then re-approved, then re-canceled, then re-approved—and successfully built and launched that they just didn’t have the time needed to create a physical artifact like a plaque or a record,” he told me. He was disappointed about that for a little while, assuming that it had to be some modern-day artifact equivalent to the Golden Record (“maybe a quantum nano superconducting
Voyager
record or something”). But then he thought more about it.
Voyager
had set
the bar high for analog, physical artifacts. Later projects, like The Planetary Society’s “Visions of Mars” on the NASA
Phoenix
lander, or the society’s other efforts to launch the signatures of thousands of people on planetary missions, advanced that technology to CDs and DVDs. “But we have never sent out a digital message,” Jon recalled thinking. “Nobody thought of putting one in the computer. So it’s kind of the next level up from the physical artifacts. Granted, the lifetime of it probably isn’t as long as the
Voyager
record, but again it’s still an important gesture. Every spacecraft leaving Earth will have some type of computer, and so we may be establishing a positive precedent with the
New Horizons
digital message, especially the crowd-sourcing aspect of it. Before, it was just a few of us who were attempting to speak for the Earth. But with
New Horizons
we’re making a serious effort to involve as much of the Earth as we can. And that’s certainly something I think Carl would have liked.”

I’m a member of Jon Lomberg’s advisory board for what is being called
the One Earth: New Horizons Message Project, and as we begin ramping up our public engagement in formulating what some are calling the
Voyager
Golden Record 2.0 message, it will be interesting to see how different today’s crowd-sourced message to the future will be from the message so carefully crafted forty years ago by a select group of people for the
Voyager
record. “Perhaps
New Horizons
will never be found and its message never read,” says Jon Lomberg, “but the very act of creating the message and sending it inspires the imagination and encourages a wider perspective in space and time. Humans have never needed this perspective more than they do today. Contemplating the vastness of the cosmos, we make our mark on it by our explorations—surely one of the most positive acts by the human species in all our
history.”

Part Two

THE GRAND TOUR

4

New Worlds among the King’s Court

N
INETY-NINE POINT EIGHT
percent of everything in our solar system is inside the sun, and of the 0.2 percent that is left, more than half of
that
is inside the planet Jupiter. Jupiter has more mass than all of the other planets, moons, comets, asteroids, and space dust out there combined, making its royal monikers from classical mythology—Zeus, Thor, King of the Planets—truly apt.

Jupiter was the first encounter for both
Voyagers
, and even after the successful
Pioneer
flybys just a few years earlier, much was still unknown and mysterious about our solar system’s largest planet. In 1610, Galileo was the first to recognize Jupiter as a world with moons of its own, and the astronomers Robert Hooke and Giovanni Cassini were the first to recognize (separately), in 1665, the famous Great Red Spot and other colorful moving zones and belts of clouds
in the giant planet’s dynamic atmosphere. Over the intervening three centuries, improving telescopic resolution and instrumentation provided more information about the speed of Jupiter’s winds and giant storm systems, of which the Great Red Spot is one, and about the chemistry of the clouds and the composition of the brightest moons. Right up until the
Voyager
flybys, however, those moons were still only points of light.

The
Voyagers
changed all that, forever. After the flybys, Jupiter’s four large moons—Io, Europa, Ganymede, and Callisto, collectively known as the Galilean satellites after their original discoverer—became distinct worlds of their own, with features and characteristics and even personalities that now make many consider them full-fledged planets. Indeed, I believe that
Voyager
’s exploration of the Galilean satellites revealed a bias that we didn’t even know we’d had in our search for life beyond Earth. The only example of life as we know it exists on a
planet
—a large body directly orbiting the sun—and a planet relatively close to the sun at that. Life on Earth takes advantage of our inner solar system location, of our abundance of liquid water, and the ample energy of sunlight bathing our planet. Therefore, why wouldn’t we think it most likely that extraterrestrial life is planet-based as well? The only large moon in the inner solar system is our own moon, which lacks an atmosphere and thus we know is lifeless. But what if there are other moons out there that might have the right ingredients—liquid water, for example, or ways to tap into enough sunlight or other energy sources like volcanoes or tidal energy—to fuel the biochemistry of life? There are more than a dozen large moons in the outer solar system. According to the official definition, moons can be only once-removed cousins of planets because they revolve around a planet instead of
around the sun. But what if that didn’t matter? What if what matters instead in the search for life “out there” is what they are intrinsically like, not who they happen to hang around with?

FLIGHT PATH

Voyager
mission designers such as Charley Kohlhase and his team of about ten colleagues at JPL had the job of figuring out how to time, align, and visualize the trajectories of each
Voyager
’s single pass through the Jupiter system so that the spacecraft would get the best possible views of the planet and its large moons, have a good communication geometry with the Earth,
as well as
have its trajectory bent and sped up by
the right amount to swing the probe on to Saturn. Physicists realized long before Gary Flandro, Charley Kohlhase, and others on the
Voyager
team that such slingshots were possible, and that they represented the closest thing to a free lunch that one could get in the solar system. By aiming a spacecraft to pass
behind
a massive planet in its orbital path around the sun, the spacecraft would not only speed up as gravity draws the craft inward toward the planet, but it would also get a boost—a gravity assist—from the planet’s own orbital momentum around the sun. It’s kind of like the way a batter adds energy to a pitched softball when she hits it. The ball does not simply bounce off the bat with the same speed in the opposite direction—
energy
supplied by the batter is
added
to the ball’s energy, changing its direction
and
increasing its speed. A planet’s orbital momentum is a source of energy that a spacecraft can tap into to speed up (or, if passing
in front
of a planet relative to its direction of motion, to lose energy and
slow down
using the
antigravity effect) relative to the sun. It seems like getting something for nothing, but it’s not. Newton’s laws of motion tell us that when it comes to forces and energies, there is always an equal and opposite reaction to any action. So for the spacecraft to speed up, it means that the planet has to slow down. Energy is conserved, never lost. The difference is, though, that because the mass of the spacecraft is so minuscule compared to the mass of the planet, the result of the spacecraft stealing some of the planet’s orbital momentum (mass times velocity) is insignificant for the planet. When the
Voyagers
did their gravity-assist slingshots past Jupiter, for example, they were sped up by about 10 miles per second relative to their approach velocity, but Jupiter itself was slowed down by only
the equivalent of about 1 foot per
trillion years
.

Setting up the flight trajectories for the
Voyagers
was a monumental task, sifting through what Charley describes as “10,000 possible flight paths” just for their primary mission targets Jupiter, Saturn, and Titan. Charley emphasizes that his team had to develop new software methods to quickly simulate and visualize many possible missions. One method included modeling spacecraft orbits using a centuries-old shortcut that broke the orbits down into shorter, simpler segments called conic sections (“Who was it, Kepler or Newton,” Charley asked himself, thinking back on the early history of celestial mechanics, “who first came up with this mathematical trick?”—it was Newton who discovered the shortcut), because traditional orbit-calculation methods would have taken months to complete if using the full calculations and the computer technology at the time. “I’ve got a bunch of mission constraints I’m trying to honor, like communications, navigation, and getting the trajectory to the next planet,” he recalls, adding wryly, “and I also know that
the scientists would rather fly by the lit side of a planet and its moons rather than the dark side. And so we’re trying to get the flybys close to these new worlds, as close as we can, but not so close as to magnify the navigation errors.”

That last part was important: they knew that Jupiter would bend the trajectory of the spacecraft by a given amount because the mass of Jupiter was well known. But they didn’t know the precise masses of the moons they wanted to get close to, and so they had to be careful not to get
too close
, lest that unknown mass bend
Voyager
’s path astray. “So we applied the engineering constraints, then what we thought would be attractive to Science.” The team would then generate those cases in reams of plots and tables and pass them on to Ed Stone’s Science Steering Committee to look over and give feedback as to the quality and scientific value of the various moon and planet geometries that these “computer-flown missions” would yield.

Charley positively beams with pride at his team’s accomplishment of finding the two perfect needles in the haystack of mission designs they started out with: “Winnowing through that list of 10,000 possible missions to find the best 110 to target and the 2 to launch was an effort done nearly perfectly. I should show more modesty than that, but we did that job right.”

The final March 5, 1979, Jupiter flyby path that Charley and Ed and colleagues on the Science Steering Committee chose for
Voyager 1
enabled close passes by Io, Ganymede, and Callisto, but only a relatively distant view of Europa. A more detailed view of Europa would have to wait until the July 9, 1979, flyby of
Voyager 2
, which made close passes by that moon, as well as Ganymede and Callisto, but allowed only distant views of Io. Thus it was only together, through both
Voyager
flybys, that high-resolution photos of all these
worlds; movies and high-resolution photos of Jupiter’s clouds and storms; and lots of other unprecedented data on radiation, magnetic fields, and the chemistry/composition of the Jovian system could be obtained.

Even at their super-high speeds of around 35,000 miles per hour, each of the
Voyagers
took about three days to pass through the heart of Jupiter’s mini solar system, traveling from the orbital distance of farthest-away Callisto to their closest approaches to the giant planet (a distance away of only about three to five times the radius of the planet), then back out again. During that time, the spacecraft was in frequent communication with the DSN, radioing
the latest images and other data back to an eagerly awaiting science team and press corps at JPL, and receiving updates to the onboard sequences with the newest team estimates of the best scan-platform pointing, camera exposure times, and other parameters.