Carl Sagan stands in front of a Viking lander model in Death Valley, California.
The late Cornell University planetary scientist, astronomer and author Carl Sagan was not only a masterful science communicator but had the gift of pushing humanity to think in innovative ways. His experiment to remotely detect life on Earth from NASA’s passing Galileo spacecraft is the stuff of legend. And we are still debating the results of astrobiology experiments that Sagan championed on NASA’s Viking landers to Mars. But a quarter century after his death, it’s hard not to wonder what he’d think about the current state of space exploration.
Somehow, I think Sagan would be extremely perplexed and ultimately disappointed in what the U.S. and its space-faring allies have yet to accomplish on three major fronts.
Firstly, we’ve yet to find evidence for life on Mars.
True, the rovers have given us tantalizing reason to be hopeful, but with each new twist and turn about the possibility of ancient or even extant water on Mars, the potential for astrobiology on the red planet becomes more convoluted.
“By the standards established before launch, two of the three [Viking] microbiology experiments have had a positive outcome-if comparable results had been obtained at some spot on the Earth the existence of a terrestrial microbiology would have been considered established,” Sagan wrote in a 1979 special issue of Michigan Quarterly Review. “But Mars is not the Earth and in particular the chemistry of the soil, bombarded by ultraviolet light from an ozone-free sky, may be very different on the red planet than it is here,” he writes.
In truth, we will have to wait on NASA’s Mars sample return missions to bring any clarity to controversy surrounding the fact that mars may have once harbored microbial life.
I also think that Sagan would be bitterly disappointed that we humans have yet set foot on the red planet.
Secondly, even though Sagan had his sights set farther afield I also think he would be disappointed that it’s been more than 50 years since astronauts have walked on the Moon.
True, NASA has plans to return astronauts to the Moon by 2025. But I’m sure that it would be difficult to find even the most sanguine odds-maker in Vegas to accept a bet that NASA astronauts would in fact walk on the lunar South Pole by then. In fact, the original much-touted landing date of 2024 has already been pushed back by a year.
And finally, in terms of astrobiology, Sagan would love the progress that we’ve made in characterizing extrasolar planets. But I think he would be bitterly disappointed at how far we must go in making radio contact with potential extraterrestrial intelligence.
If Sagan were alive today, I’d wager he’d be advocating whole new means of looking for extraterrestrial intelligence in ways that few of us could have imagined only a couple of decades ago. Sagan would probably be emphasizing new means of looking for exo-civilizations in the optical spectrum and would likely embrace the new science of looking for evidence for extrasolar civilizations via their own technosignatures.
Although Sagan was an avowed advocate for robotic exploration of the cosmos, I do wonder what he would say about our seeming continuing lethargy in sending humans beyond low-Earth orbit and cislunar space.
“Before we go looking for [life] elsewhere, we need to be certain that we can identify life from space,” I noted in my 2001 book Distant Wanderers: The Search for Planets Beyond the Solar System. In 1990, [Sagan] led a team that used NASA’s Galileo spacecraft and atmospheric probe to prove that life here on Earth could be detected from space. In December 1990, the spacecraft’s sensors detected abundant gaseous oxygen, ozone levels more than 20 times normal for a planet with no life, and methane at levels of one part per million, about 140 times more than expected without some underlying biological activity, I noted.
But detecting life spectroscopically on a far-flung planet is no easy feat and with each passing year, a whole new generation of astrobiologists continually come up with reasons why astronomers might detect false positives in the spectra from an earthlike planet circling a nearby star. And one wonders what Sagan himself would have to say about such prevaricating. Would he say enough already; we’re being too cautious in making judgements about finding life remotely? Or would he wholeheartedly support such cautious thinking?
I can’t answer that. But without Sagan and others like him prodding us to think outside our narrow astrobiological paradigms, finding evidence for life beyond our own Earth will continue to be nigh on impossible.