Most speculation about directed panspermia falls under two umbrella questions: Could an intelligent species seed an Earthlike planet with life? And could humans do the same with a clear conscience?
If panspermia occurs naturally, as many argue that it does, then panspermia aided by technology should be that much more effective, and thus that much more common. After all, if alien bacteria can make interplanetary journeys on their own, then they can certainly do it with help yet no evidence of directed panspermia has ever been discovered. Opponents of panspermia (or at least those who maintain a belief in extraterrestrial intelligence) claim that by simple contraposition, this lack of proof proves that panspermia “doesn’t work.” However, due to the (apparent) scarcity of technologically advanced societies in our sector of space, an absence of evidence for directed panspermia does not necessarily mean that it is impossible only that no nearby alien civilizations are putting it into practice.
The intentional propagation of microbial life throughout space does indeed seem to be possible. In science fiction directed panspermia is usually the work of a species far more advanced than ours, but the reality is that panspermia could likely be initiated using today’s human technology. Capsules on the order of a few millimeters or centimeters could conceivably carry Earth bacteria to other star systems using an efficient solar sail propulsion system. They might take hundreds of thousands of years to arrive at their destination, and many would perish on the journey, but the process is definitely within reach.
Human-initiated panspermia is, of course, a highly controversial proposal, with strong feelings on both sides. On one hand, the most popular argument in favor of the colonization of other planets is to have a “backup” in case of disaster on Earth: so as a means of making a planet habitable for human life, directed panspermia might be a simpler and far cheaper alternative to terraformation (albeit a far more gradual one). On the other hand, propagating Earth life elsewhere in the galaxy could annihilate existing biospheres, in the same way that an invasive plant species can drive a native one to extinction. Though we do have the technology to disperse life, we aren’t capable of detecting it from afar, meaning that any panspermia campaign could have this effect. Even in the far future, with hypothetical technology capable of detecting evidence of microbes on planets lightyears away, this could prove an ethical problem. Humans could confirm the absence of life on a planet and send biological capsules its way; but there is no guarantee that life would not evolve during the long interval between the capsule’s launch and its arrival. To sidestep this problem, some have suggested targeting newborn stellar systems, where life would not have time to evolve.
The problem with directed panspermia is that almost all of the factors that would help us through this ethical dilemma are unknown. Nobody knows for certain how life originates, or how often, or where (let alone why) . Though human tendency in similar situations has historically been to “go ahead and do it anyway,” in this case the morally minded can breathe a sigh of relief: the technology exists, but the monetary cost of launching a fleet of biological capsules is still prohibitively high for those who would like to do so.
Gilster, Paul, “Seeding the Galaxy” -- http://www.centauri-dreams.org/?p=11334
Makukov and shCherbak, “Space Ethics to Test Directed Panspermia,” Life Sciences in Space Research, July 2014
The Interstellar Panspermia Society, “Principles of Panbiotic Ethics”-- http://www.panspermiasociety.com/ethics.php
- Emma Flickinger