What will aliens think of the messages we leave for them?
The New Horizons spacecraft was a unique mission. For the first time since Pluto was discovered by Clyde Tombaugh in 1930, the mission aimed to actually visit the planet and study it up-close.
The journey to Pluto is a long one: the lonely planet lies an average of 5.9 billion kilometres away, or about 40 times the distance from the Earth to the Sun. New Horizons, launched from our planet in 2006, had to journey through space for nearly a decade to reach its destination. Over these distances, radio signals dwindle to tiny rays of information among the noise, and the time lag means that most of the spacecraft’s operations have to be autonomous. The Sun itself, so very far away, looks like nothing more than an unusually bright star, barely enough to keep the solar panels going.
Having sent their spacecraft so far away, the scientists in charge of the mission decided to push forward, beyond Pluto, into the Kuiper Belt, and— eventually—into interstellar space. They decided to leave mementos of Earth on the craft in hopes that an extraterrestrial being would find the spacecraft and decide to investigate. Some of these included a compact disc containing 434,738 names, a piece of an ancient aircraft, a stamp that ground some scientists’ gears, Tombaugh’s ashes, and the flag of the United States.
One wonders, though, how impactful those mementos would actually be.
Imagine the New Horizons spacecraft continuing along its interstellar journey for a billion years and eventually crashing into a habitable planet around a distant star. Its equipment would be defunct by then, just a piece of space junk composed of heavy elements with a rough surface cratered by numerous impacts of interstellar dust, gas and cosmic-ray particles.
Now imagine the astronomers on that exo-planet discovering this technological junk as it approaches them under the lamppost of their parent star which illuminates the darkness around them. They use their most advanced telescope to survey the sky for objects that may impact their planet, a warning system to avoid catastrophes from space rocks. But this object does not appear to behave like a common asteroid or comet that they had seen many times before. In particular, the object has no cometary tail and yet it appears to be pushed away from the star by a force that declines inversely with distance squared because of the star’s radiation pressure on its walls.
After hearing a colloquium about the anomalies of this object, one of the experts on space rocks states: “this object is so weird, I wish it never existed.” Other experts choose to write a review article in a prestigious journal and argue that this must be a natural object and there is no reason to suspect anything else based on their vast knowledge on space rocks.
Months later, a team of other experts argues that this object is a rock of a type that they had never seen before, namely a hydrogen iceberg, and this is why the cometary tail is invisible. Another team suggests that the object is a dust bunny, pushed by light. And a third team of experts argues forcefully that it must be a nitrogen iceberg, chipped off the surface of a distant planet.
The consensus among all experts is that even though the object is heading on a collision course with their planet, nothing should be done to deflect its trajectory because all the likely explanations for its origin: a hydrogen iceberg, a fluffy dust bunny or a chunk of frozen nitrogen, imply that the object will burn up quickly high up in the atmosphere of the planet and nothing will survive to damage the surface.
The most sophisticated government satellites monitor the plunge of the object into the atmosphere. They reason that their data could decide which of the three explanations by the experts is the correct one, based on how quickly the object burns up and which gases are prominent in its fireball.
As New Horizons crashes into the planet’s atmosphere, it defies all expectations. The fireball occurs at a much lower altitude than expected for a dust bunny or for exotic icebergs.
The light curve from the meteor in the lower atmosphere implies that the meteor’s composition was much tougher than a common rock. Its material strength is far greater than that of any stony meteorite, not to speak about a dust bunny or exotic icebergs.
The astronomical community refuses to believe the government’s data, because it does not include measurement uncertainties. These uncertainties are classified for national security purposes, because the sensors used to collect the data are classified. After three years, the government issued a letter, along with the fireball light curve, stating that the object is highly unusual in its composition at the 99.999% confidence. In response, experts are widely cited in newspapers as saying that a letter from the government is not the way science is done and since the actual data is classified – they will never know what it means.
Some time later, after all the hype has died down, a small group of scientists decides to scoop the ocean floor at the impact site and search for meteor fragments that survived the fireball. When they conduct the expedition, they find on the ocean floor a small box that was attached to the New Horizons spacecraft. The box contains thirty grams of the ashes of Clyde Tombaugh, a “human” who discovered a planet called “Pluto”. They immediately conclude that the interstellar meteor must have been a technological relic of a so-called “human civilization” that launched it a billion years ago.
And they also argue that this “human civilization” was not particularly intelligent because it destroyed the genetic information about the person it wanted to commemorate. Tombaugh’s DNA was burned up into ashes that are no different from the ashes of cigarette. This implies a primitive ritual that makes little sense for an intelligent science-based community. “If humans are still out there, we want nothing to do with their destructive mindset”, they conclude in their report. End of story.
The above storyline is anchored in facts. Anyone who knows me would testify that I do not like science fiction.