This week we all had a good laugh at the expense of Rep. Dana Rohrabacher (R-Calif.), who asked NASA scientists during a committee hearing whether it was possible that a civilization existed on Mars thousands of years ago. "Would you rule that out?" he asked. "See, there's some people... Well, anyway."

Rohrabacher is an interesting figure in Washington, whose once-idiosyncratic views seem largely in vogue with those of the new administration. Politico called Rohrabacher "Putin's favorite Congressman" in a mini-profile last year. Like Trump, the Congressman has also called climate change a hoax. In a 2014 letter to President Obama, Rohrabacher wrote, "Mr. President, we both know I have referred to the theory of man-made global warming as a 'hoax,' and, yes, I once used the phrase 'dinosaur flatulence' as a soft jab at what I considered to be climate alarmism."

So after Rohrabacher's question—which seemed driven by some arcane conspiracy theory given his use of "some people"—it was curious that one of his few defenders was a well-known climate scientist, Gavin Schmidt. "To be fair, NASA astrobiology is very interested in this (and similar) questions. Not sure why it's out-of-bounds to ask," the NASA climate modeler wrote on Twitter.

It's true that some scientists have considered the possibility that a technological species could have existed in the Solar System prior to humanity's rise on Earth. For example, last year, Penn State astronomer Jason T. Wright authored a paper that discussed possible origins and locations for "technosignatures" of such a civilization. Other astronomers have suggested looking for lights on Kuiper Belt Objects that "may serve as a lamppost which signals the existence of extraterrestrial technologies and thus civilizations."

A Solar-System-wide cataclysm?

In his review, Wright doesn't dismiss the possibility of earlier technological civilizations on Earth, Venus, Mars, the icy moons of the outer Solar System, and other locations. He then investigates the likelihood of any artifacts remaining from those civilizations (low on worlds such as Venus and Earth, higher for places like Mars) today. Wright also considers why such past civilizations may no longer exist today.

"The most obvious answer is a cataclysm, whether a natural event, such as an extinction-level asteroid impact, or self-inflicted, such as a global climate catastrophe," Wright asserts. "In the case of a prior space-faring species that had settled the Solar System, such an event would only permanently extinguish the species if there were many cataclysms across the Solar System closely spaced in time (a swarm of comets, or interplanetary warfare perhaps), or if the settlements were not completely self-sufficient. Alternatively, an unexpected nearby gamma ray burst or supernova might produce a Solar-System-wide cataclysm."

Clearly, with this research we are well into the realm of speculation. While it is true that we have no way but radar mapping to explore the surface of Venus, humans have extensively explored our own planet and placed a number of rovers on the surface of Mars. For all of this, there is not a shred of evidence that advanced civilization has existed anywhere in the Solar System but Earth during the last few millennia.

From a purely scientific standpoint, it's a perfectly reasonable question to ask whether life may have existed elsewhere in the Solar System, or does today. That is, increasingly, one of NASA's raisons d'être. But when a Congressman asks about such a civilization existing thousands of years ago on Mars, and attributes the question to "some people," it's justifiable to hold the question up to scrutiny.