Be forewarned: this story may not exactly match the scientific facts. I read a cool article about Proxima Centauri b, and this story is based on that article. But I can't find the article right now, and my muse is screaming at me to write the story. I've checked my facts against other sources, and they look solid. But in case they aren't, I take my cue from the Prezzynited States, who never lets the facts get in the way of a good story.
Proxima Centauri b was discovered in 2016. It was a planet a whole lot like earth, orbiting in the habitable zone of a red dwarf called Proxima Centauri. Proxima Centauri itself was involved in a slow and intricate dance with a double star called Alpha Centauri, and for the next few thousand years, they would be the closest stars to Earth. Proxima was the closest of the three, hence its silly name.
The three stars were in the constellation Centaurus, visible only in the southern hemisphere. To the naked eye, the Alpha Centauri twins appeared as one bright star, the brightest star in the constellation; hence, they received the designation Alpha. Proxima, being a red dwarf, was not even visible to the naked eye. Astronomers had discovered it in 1915 by very carefully examining photographic plates.
The planet was discovered by astronomers using the radial-velocity method of planet-hunting. It was given the designation "b" because, in exoplanetary exploration, "a" is always reserved for the parent star.
Being only four light-years away from earth, Proxima b excited the imagination of amateur space explorers all over the world. Three billionaires, two of whom happened to own rocket companies, decided to pool their fortunes and sponsor a take-pictures-and-return mission to Proxima b.
Warp drive and hyperdrive were still just science fiction when they got started on it. They approached the directors at the Jet Propulsion Laboratory, in Pasadena, California, with bags of money and their crazy idea. JPL did a preliminary design and came back to the billionaires with a schedule and a price tag, and the billionaires said, "Okay, let's do it."
And so, after seven years of design, construction and testing, two unmanned probes were launched atop giant rockets from a spaceport in Odessa, Texas. By the time the conventional rockets burned out, the pair were aiming for a rendezvous with Jupiter, and then with Saturn, counting on a slingshot boost from the gas giants to augment their ion drives and give them enough velocity to escape the Sun's gravitational pull and follow their ancient brethren out into deep space, directly towards Proxima b.
The two probes were named Lewis and Clark. The first probe, Lewis, was larger and heavier. It contained more instruments and had a more powerful computer. It would be used on the journey to take pictures of the Centauri trio, solve the four-body problem involving three stars and one planet, calculate a navigation solution, and transmit the solution and some of the star pictures to the second probe, Clark. As the pair approached Proxima Centauri, Lewis would do an extensive analysis of the star (or stars, if the Alpha twins were in the right place), transmit its data to Clark, and then go shooting past, in the general direction of the Andromeda galaxy.
The second probe, Clark, was lighter than Lewis. Its instrument suite included cameras and filters, a gravitometer, a magnetometer, and not much else. Its computer wasn't as powerful as Lewis' computer, which is why they would travel in formation, never more than a hundred kilometers apart, all the way to the Centauri cluster. But while the bigger, heavier Lewis would continue in a straight line, Clark would use the navigation solution downloaded from Lewis to swing in a tight parabola around Proxima Centauri, then buzz the planet Proxima b, taking pictures like a mad tourist, and then fly home.
Instead of a massive instrument cluster, the largest part of Clark's payload was a nonvolatile memory bank. Constructed of copper and cobalt, its memory density was somewhere between a 1990s-era hard disk and a 2020s-era flash memory, but it was indestructible: once it was written, the only thing that could erase it was an oxidizing flame hot enough to melt the alloy. Not even a fiery re-entry through Earth's atmosphere could damage it. And that was the plan.
Although there was a throttle on the ion engines, they were designed to run at full blast for up to 80 years. Mission planners had calculated that it would take Lewis and Clark 38 years to reach the Centauri cluster, and another 38 years for Clark to complete its solo trip home. By then, the billionaires would be long dead, as would the scientists at JPL who built the probes, and their children. It would be up to the grandchildren of the billionaires and the rocket scientists to welcome Clark home.
* * *
Like a fisherman's wife waiting on her balcony, a small and select group of astroscientists waited for Clark's return. The billionaires had commissioned a radiotelescope near Montevideo, Uruguay, to do nothing but stare at Proxima Centauri for 80 years. They had endowed a whole department at JPL to stand vigil. For the first ten years, the radiotelescopes would call out "Marco" to the heavens, and the probes would reply with their "Polo" responses. As the years passed and the ion drives pushed the probes faster and farther, the interval between "Marco" and "Polo" became longer, and the signals became fainter, until finally, when the interval was 2.3 years, the explorers were more than halfway to their destination, and their signals were too faint to pick up anymore. The department at JPL shrank to one endowed chair.
Lewis and Clark were on their own. If things went according to plan, Lewis would never be heard from again. But the dish would keep calling "Marco" to the heavens. And a succession of interns at JPL would sit at a desk, working on their intern projects, which would include babysitting the waterfall display which would one day signal the return of the interstellar fisherman.
* * *
Math! I needed to put this here so I could keep my dates straight
2016 - Proxima b descovered
2028 - Lewis and Clark launched
2038 - radio contact lost with Clark
2066 - Clark reaches Proxima b, but humans have no way of knowing
2094 - radio contact reacquired with Clark
2104 - Clark returns
* * *
In 2094, JPL was still around. It was still ostensibly a research laboratory, as it had been in the days of the old NASA, but now it was making good money, sending unmanned spacecraft scooting along the convoluted pathways of the Interplanetary Transport Network, and parking its deep-space communications relays in the same solar orbits as Mars, Jupiter, and the inner edge of the Kuiper Belt. But the billionaires' endowed chair for the Proxima b Watch was still there, and in the summer of 2094 it was manned by an intern, a bored aero/astro student who, once a week, connected with the dish in Montevideo, ran the diagnostics that ensured the system was still working, stared at the waterfall display for an hour, and then gave up and went back to more interesting work.
Then, one day, there was a blip.
Twenty years earlier, in 2074, another intern (who, by sheer coincidence, was this bored aero/astro student's mother) had mounted a big red incandescent light bulb on a pole, and screwed the pole to the side of the Proxima b Watch desk. She had added a few lines to the Watch program so that the light would blink if the dish in Montevideo detected a "Polo" signal. Since then, the computer running the Watch program had been replaced several times, but the red light was still there, still in good working condition - and it had never blinked.
So in 2094, our bored intern was sitting at her desk, calculating trajectories for the mining equipment JPL was going to ship for Ganymede, when suddenly, the red light turned on.
The reactive, instinctive part of her brain caused her to look at it in annoyance, assuming that it was a malfunction.
Then the slower, more deliberate part of her brain announced that the Watch program had never malfunctioned before. She opened the waterfall display.
And there was a blip, right where the Polo signal belonged. She screamed. Clark was coming home.
* * *
As on the outward journey, the signal was very faint - but it was strong enough for the JPL scientists to calculate that Clark was still over 2 light-years away, and even at its amazing approach speed, it would be another ten years before it got to earth.
But there was a problem. The probe was going so fast that it would shoot past the earth, past the sun, and right out the other side of the solar system. They had to find a way to slow it down, and either capture it in space or crash it onto Earth, someplace where they could find it.
The old mission documents were dug up, dusted off, and the math rechecked. According to the documents, the re-entry was all preprogrammed. Clark would flip, end for end, about the time it crossed the Kuiper belt, so that its ion engine, still firing full blast, would act as a retro-rocket. About the time it crossed the orbit of Mars, it would be crawling along at Earth-capture velocity. However, the JPL scientists reached out and reprogrammed Clark's reentry sequence, so that as long as the Earth was in the right place, Clark would slip into orbit around it, and space technicians could pull it out of the sky and gently carry it the rest of the way home, instead of following the original mission plan and letting it crash clumsily into the planet.
* * *
Finally, in 2104, Clark was perched in a clean room at JPL. Its leading surfaces were pocked and pitted from the space dust that had smashed against it, like bugs on a cosmic windshield, as it had flown through space at 74 million miles per hour. Compared with modern unmanned space vehicles, it was an antique. The JPL scientists looked at it and wondered how it had ever managed to stay aloft, it was so primitive - so heavy - so ungainly. The fact that it had performed flawlessly, continuously, for its full 76 years, left them in awe of the skills of their forefathers.
The copper-cobalt memory was reverently extracted from the chassis. The scientists looked upon it the way their grandfathers had looked upon Thomas Edison's wax phonograph cylinders, knowing that in this ancient storage device were the first close-up pictures of another world.
It contained more than that, however. Lewis and Clark had kept a careful log of more than just pictures, and Clark had faithfully brought it all home. Connected to a modern computer, the memory bank gave up its secrets, and hour by hour, day by day, the world was amazed by the new data that streamed from Pasadena.
Lewis had taken enough photos of the dance between the three stars for scientists to put together a time-lapse animation of it. Lewis had gotten photos of the surfaces of all three stars, pocked with sunspots and laced with ribbons and arches of incandescent gas. Lewis' spectophotometric analysis of the stars had confirmed some theories, blasted other theories, and given astrophysicists a lot more to chew on - the first close-up photos of another star, times three!
As astronomers pored over Lewis' images, they discovered that Proxima b had siblings, and so Proxima Centauri c, d, e, f, and g were added to the family. Two were rocks, and three were gas giants whose orbits were strongly influenced by the Alpha twins.
Lewis had fed Clark navigation data so exact that Clark had passed within 200 miles of the planet Proxima b's surface - a near-collision. Clark's stereoscopic cameras had taken pictures at a prodigious rate. Its radar and its magnetometer had mapped three fourths of the planet in its single flyby. Its spectrophotometer had detected some sort of red-light photosynthesis on the surface, and its mass spectrometer had captured a few stray molecules from the planet's atmosphere: heavy in CO2, O2 and argon.
Proxima b is tidally locked with its star, meaning that the same side always faces the star, just like earth's moon. But the dark side is not really "dark", since the Alpha Centauri twins light up the dark side for half of every planetary day. Clark was therefore able to get some pictures of the dark side, a mosaic of starlit twilight and classic inky blackness.
Some of the JPL staff were disappointed that, while there were clear signs of plant life on the sunny side, there was no sign of animal life anywhere, or of the artificial light that would serve as a sure sign of animal life or an advanced civilization. One technician posted a sign above his desk, saying: "Fermi is still right."
* * *
And that was the end of the first Proxima b expedition. Launched in the hiatus following the first International Space Station, it ended during the heyday of the planetary mining period, when robotic mining colonies were operating profitably around the solar system. Like a wagon train pulling into a modern city with skyscrapers and electric lights, Lewis and Clark were the bridge between two different eras of space exploration.
POSTSCRIPT: In January 2020, scientists announced that they had found a second planet orbiting Proxima Centauri. I could add this to the story, but I won't.
