Imagine that, in the future, astronomers make the historic announcement that they’ve discovered a second Earth orbiting a star a few light-years away.
Using an advanced exoplanet-hunting space telescope, the hypothetical team of planet hunters reports that they’ve been watching the silhouette of a small rocky world drift in front of its host star. These transits reveal the alien world has an orbital period slightly shorter than Earth’s, but as the star is slightly dimmer than our Sun, the planet is orbiting right smack-bang in the centre of the star’s habitable zone.
In this hypothetical future, astronomers have not only gone on the record to say that this exoplanet appears to be of a similar size to Earth, it’s also at just the right distance that, if it does possess water, that water could be at just the right temperature to exist in a liquid state. This is exciting, but only suggestive of a bona fide “Earth-like” planet. So, in follow-up studies astronomers use another exoplanet-hunting technique to reveal more characteristics of this interesting planet.
By using a high-resolution spectrometer on a ground-based observatory, a collaborating team of astronomers confirm another profound thing about this world. As it orbits, the planet exerts a slight gravitational tug on its host star. This tugging is revealed as a tiny shift in wavelength of light the observatory sees coming from the star as it moves slightly towards and away from us – the amount of star “wobble” relates the the planet’s mass. The blue-shifting and red-shifting of starlight reveals that the world is of a similar mass to Earth.
|Space tourism industry targets Asia’s wealthy|
Using the “radial velocity method”, combined with the “transit method”, the international collaboration feverishly takes further observations, refining their measurements of this increasingly interesting world. Papers are published and the science media starts to run a few stories about this intriguing world – while avoiding, at all costs, any mention of the phrase “Earth-like”.
By this point in our hypothetical future, thousands of exoplanets have been detected in our galactic neighbourhood and hundreds of them orbit within their stars’ habitable zones. A few dozen appear to have more than one Earth-like characteristic, but none can be called genuinely “Earth-like”. They could be dry and barren like Mars or have atmospheres as thick and hellish as Venus – two planets, by the way, that orbit inside our solar system’s habitable zone.
So, our hypothetical world is not “Earth-like” yet. Yes, it’s “Earth-size”, “Earth-mass”, has similar orbital characteristics as Earth and orbits a Sun-like star, but no science journalist worth his or her salt will go on record as saying it was remotely “Earth-like”.
But then comes the announcement of the century.
Using a next-generation space telescope, days of observing time are committed throughout the exoplanet’s orbit. As the world orbits its host star, starlight scatters, refracts and reflects, some wavelengths of which are absorbed by the chemical components inside the world’s atmosphere. The light the space telescope receives is split into its component parts and an absorption spectrum is revealed. This high-resolution spectrum acts as a fingerprint for the world’s atmosphere, each dark band representing a chemical and its abundance.
Complex algorithms are run on these data and compensations are made for observational error and any obscuring effects by the star or the intervening interstellar medium. The results from this analysis are startling. The planet has a nitrogen-rich atmosphere, is abundant in oxygen and appears to have interesting quantities of carbon dioxide, water vapor and methane. In short, this atmosphere is looking rather Earth-like.
Quickly, SETI programs focused their radio antennae and optical telescopes on this new target in the hope that some advanced alien race may have evolved there, but no radio transmissions or laser beacons are detected that betray their presence.
Astrobiologists jump on the reams of data spewing from the intense scrutiny of this fascinating new world. They ask: What‘s generating the methane? Is it biological or volcanic in origin? Is there some kind of biological process generating the oxygen? If there’s water vapour in the atmosphere, are there also oceans? Could this be a biosphere capable of supporting Earth life?
By this point, science journalists are not ashamed in calling this world “Earth-like”. Humans, barring any unforeseen surface toxin or indigenous predator, could live there. Scientists continue to urge caution, however, but their arguments are drowned out by a wave of public obsession over “Earth 2.0”.
So far, we’ve been discussing a future that could play out in the next decade or so. Granted, the chances of finding a genuine Earth-like exoplanet orbiting a star a few light-years from Earth are slim, but given the mind-boggling variety of exoplanets discovered so far, it’s far from impossible. Also, we, as a race, are reaching an interesting technological crossroads – could the discovery of “Earth 2.0” coincide with humanity’s ability to push deeper into space? Could that Earth 2.0 spur global collaboration on space technology development in the hope of eventually travelling to that fascinating destination?
|Chile telescope unveils depths of universe|
At the first Icarus Interstellar Starship Congress in Dallas, Texas, on August 15-18, nearly 200 engineers, scientists, astronomers, enthusiasts, economists, architects, artists, biologists and explorers met to discuss our interstellar future.
To many, this meeting may seem a little premature. It is, after all, 42 years since the last man walked on the Moon. Exploring interplanetary space is hard enough; travelling to another star seems pure folly. But the Starship Congress wasn’t just about sending robots and, eventually, humans to the stars; it was about the technological and cultural shifts that need to happen along the way. Also, to make anything interstellar possible, we need to use the solar system as a resource, meaning we need to build an in-space infrastructure, invest in planetary science, build settlements on Mars and boost planetary sciences, for example. Through this development, the spinoffs will undoubtedly invigorate society and inject our planet with new wealth – intellectually and economically.
Advanced propulsion systems were also discussed – after all, the space between the stars is mind-bogglingly vast, so we’d need to use transformative technologies to make the trip possible. In the near term, spacecraft that use pressure from the Sun’s light to accelerate to the outer solar system (solar sails) and others that act as “beam riders” (i.e. sails propelled by lasers strategically placed throughout the solar system and beyond) to fly through interstellar space at a small percentage of the speed of light were investigated – both of which, assuming sufficient funding, are technically feasible in a few years.
Of course, more advanced and hypothetical propulsion systems were also investigated, such as fusion-propelled starships and warpships, though those technologies are likely decades to centuries away – some may even be impossible. But then there are always the unforeseen technological leaps we might make along the way that unexpectedly accelerate our progress in ways we would never have dreamed.
The philosophical arguments for and against spreading the human race into the galaxy were also discussed in depth, as was the inevitable question: What if we come face-to-face with extraterrestrial life? Although it is highly unlikely that we will meet an alien race at the same technological level as us (our galaxy is more than 13 billion years old, many civilisations will have come and gone and developed at a different pace – if indeed they are or ever have been out there), it was generally agreed that strict guidelines would need to be drawn up before we made “first contact”. As argued by advanced propulsion expert Richard Obousy, co-founder of Icarus Interstellar (the non-profit that organised the Starship Congress), trying to make contact with a more advanced (and possibly aggressive) alien race would be extremely irresponsible. Risking first contact could result in the annihilation of humanity. When faced with a risk as extreme as this, perhaps it would be better to “act stealthily”, as breakthrough propulsion physicist Marc Millis, of the Tao Zero Foundation, commented.
The economic drivers of space exploration were also discussed in depth. Now that the technology is becoming more feasible (although there is still a long, long way to go), companies such as Planetary Resources and Deep Space Industries intend to begin tapping into the bountiful array of precious metals and rare minerals in the solar system’s asteroids.
Riding on the recent successes of the commercial space launch sector in the US, perhaps the time is right for us to be discussing an industrial infrastructure in space.
Can we afford to wait?
But the human race is notorious for being a myopic civilisation – anything beyond the next political cycle or short-term profit often isn’t thought to be worth the investment. But, according to delegates of the Starship Congress, demand for striving toward an interstellar target may not come from an economic driver at all; it may come from the public’s desire to send an expedition to an Earth 2.0.
Will humanity see the bigger picture and fulfill our interstellar potential? Or are we doomed to wrap ourselves in politics, doomed to hold onto an economy based on scarcity and fear?
Although NASA’s Kepler space telescope was recently scuttled by a faulty reaction wheel, thereby scrapping its historic exoplanet-hunting mission, its discovery of small rocky worlds proved that far from being rare, multi-planetary systems seem to be very common. That single mission has transformed the way in which we view our galaxy, and follow-up missions – such as the next-generation NASA exoplanet-spotting space telescope Transiting Exoplanet Survey Satellite (TESS) – may discover that Earth-sized world, with an Earth-like orbit around a Sun-like star. All we would then need is a sufficiently advanced observatory capable of fingerprinting that world’s atmosphere.
Although planning for an interstellar mission, whether it be manned or robotic (or both), may appear to be preemptive, many examples through history have shown us that long-term projects can be sustained. The European cathedrals in the Middle Ages and the Egyptian pyramids are two examples of long-term, often multigenerational efforts. The valuable spin-offs from President Kennedy’s promise to get man to the Moon within a decade spawned quick technological benefits and educational gains in the US. The “space race” between the US and Russia saw rapid developments in space assets.
Granted, many of these examples were driven by religion, faith and strategic prowess. But given a distant goal of Earth 2.0, could humanity begin planning for an interstellar mission? The challenge is formidable, and solutions would need to be found to the many problems here on Earth 1.0 before we can become a spacefaring race.
The Earth 2.0 incentive for interstellar exploration is potent, but of more immediate concern is that we are living on borrowed time. Living on a single planet with limited resources and a booming population can only have one outcome.
Will humanity see the bigger picture and fulfill our interstellar potential? Or are we doomed to wrap ourselves in politics, doomed to hold onto an economy based on scarcity and fear? Only time will tell.
Follow him on Twitter: @astroengine