The task for astrobiologists searching for evidence of extrasolar microbes is as uncomplicated as imitation. Primitive life forms should exist in physical conditions that were raised in a natural environment similar to that on Earth. That's why astrobiologists plan to look for molecular products of known microbes on rocky exoplanets with atmospheres in the habitable zone of their host stars.
The most recent Decadal Survey in Astrophysics of the National Academies, Astro2020, recommended a 6-meter space telescope operating in the infrared, optical and ultraviolet bands, capable of high-contrast imaging and spectroscopy. This device is scheduled to be launched by NASA in the 2040s Habitable Worlds Observatory will be designed to search for spectroscopic biosignatures of microbial life on approximately 25 exoplanets in habitable zones, and will likely cost more than $10 billion.
Where to look becomes more subtle for knowledgeable life, as they can move and spread beyond their home exoplanet. Almost all life forms, on Earth and beyond, are now extinct. Those who survive the longest on our space street may have done so by escaping their home planet on artificially created space platforms to avoid the existential risks of local catastrophes.
Although nature is often seen as a blessing, it can also be a curse. For example, there is sturdy evidence that the Earth's surface was almost completely frozen and no liquid water entered the atmosphere during cryogenic period, over 650 million years ago.
Throughout Earth's history over 99.9% of over 5 billion species that ever lived are extinct. Some of these species have been wiped out by well-documented disasters such as Cretaceous-Paleogene boundary an event that was probably triggered by the impact of the Chicxulub meteorite, which eliminated 75% of plant and animal species on Earth, including non-avian dinosaurs. However, most extinctions may have been the result of natural evolution, in which the livelihoods of some species were destroyed by change and unfavorable competition. The situation is reminiscent of political views losing their livelihoods after a devastating presidential election.
The typical lifespan of terrestrial species is 1–10 million years. This is an compelling fact because humans evolved from great apes through the hominin lineage, which emerged 5–7 million years ago. With these facts in mind, the human species is approaching the end of its natural life expectancy. Will technology save us?
While technology can delay existential threats from a snowball or a globally warming Earth, the evolution of the host star itself puts a time limit on the ability of a natural nuclear furnace to sustain life on the planet. Most stars were formed billions of years before the Sun, and the Sun will do so boil all the oceans on Earth within a billion years. Aware of this and other existential threats, a sufficiently advanced technological civilization would prefer to emigrate from its place of birth. This rationale inspires Elon Musk vision occupy Mars and make humanity a multi-planetary species.
However, once a technological civilization develops the ability to migrate beyond its birth planet, it may also be able to pursue its goals away from its host star on an artificial space platform, potentially powered by its own source of nuclear energy. This could significantly extend the most critical parameter of the Drake equation, namely the lifespan of a technological civilization.
Traditionally, the search for extraterrestrial intelligence (SETI) has focused on the neighborhood of stars. However, once technology enables escape from natural habitats, it will all come to an end. Space platforms carrying biological beings or artificial intelligence equipment can be found everywhere. Technological probes capable of self-replication could fill interstellar space in less than approx several billion years using conventional chemical propulsion.
Given this, it makes most sense to start looking for technological remnants near the nearest beacon, our Sun. Here's the reasoning Galileo projectwhich, under my direction, searches for technological artifacts in the Earth's orbit around the Sun. Our research team is working on a fresh one observatory at Harvard University and is building two additional observatories in Pennsylvania and Nevada. My students and postdocs also plan to analyze future data from the Rubin Observatory in Chile and the Webb Telescope in the coming years. We hope to finally conduct expeditions in search of materials from interstellar meteor crash sites.
What other civilizations have accomplished may be beyond our imagination. Therefore, it is best not to predict what we might find, but instead look for unknown objects that are not the product of man-made technologies.
We must hedge our bets in the search for life. This means investing billions of dollars not only in searching for biological signatures of microbes in the atmospheres of exoplanets, but also in searching for technological artifacts arriving near the Sun from interstellar space. Thanks to all these efforts, the keys of life will first be found near the nearest lamppost on our cosmic street.
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