Let’s go to Mars!

I started work at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, in November 1990. Not counting the two years I spent as a postdoc, it was my first job, and it lasted seven years.

Looking back, the 1990s were perhaps an anomalous period in NASA’s history. Space shuttles flew 63 missions during the decade and assembly of the International Space Station began in 1998. But it was NASA’s unmanned scientific missions that, in my view, characterized the space agency in the decade of Bill Clinton, Boris Yeltsin, and Jiang Zemin.

The Cosmic Background Explorer measured the spectrum and spatial distribution of the cosmic microwave background with unprecedented accuracy. That coup de recherche ushered in a new era of precision cosmology and earned Nobel Prizes in 2006 for COBE‘s two principal investigators, John Mather and George Smoot.

From 1990 through 2000, the Compton Gamma-Ray Observatory mapped and characterized the high-energy cosmos. Its instruments discovered hundreds of new sources. Data from CGRO proved that gamma-ray bursts originate at vast distances outside our galaxy and therefore release more explosive energy than any other phenomenon in the universe.

Barring the losses of Mars Observer due, most likely, to a fuel-tank explosion and Mars Climate Orbiter due, embarrassingly, to the inconsistent use of Imperial and metric units, NASA’s planetary probes also had a good decade. Launched in 1989, Galileo arrived at Jupiter in 1995 and spent the next seven years studying the gas giant and its moons. Mars Global Surveyor mapped the red planet’s surface, revealing features that looked as though they’d been formed by the action of liquid water.

Of NASA’s 1990s missions, the Hubble Space Telescope, which remains in orbit, loomed largest. Once the telescope’s faulty optics had been fixed at the end of 1993, the observatory went on to make a string of discoveries. The two deep fields of 1995 and 1998 showed that galaxies in the early universe look very different from their mature counterparts in the local universe. Before HST, astronomers knew that the Hubble constant was somewhere between 50 and 90 km/s per megaparsec. HST determined it to be 72 ± 8 km/s/Mpc.

I’m not sure whether the general public was as excited by the discoveries as my fellow astronomers and I were, but HST‘s images of nebulae, galaxies, and other photogenic cosmic objects became iconic artifacts of popular culture. In the absence of manned missions outside low-Earth orbit—an absence that has lasted 41 years—NASA stopped being an exploration agency to become what it remains today: a science agency.

Although I’m happy that NASA continues to fund unmanned science missions, the agency also needs an ambitious program of human spaceflight. The discoveries in the 1990s of dark energy and the first exoplanets were momentous, but nowhere near as inspiring as Neil Armstrong’s first steps on the Moon or even, perhaps, as the late Sally Ride’s first spaceflight in 1983.

Unfortunately, as many commentators have observed, NASA lacks a visionary mission. Returning to the Moon or landing on an asteroid doesn’t qualify. NASA should aim at Mars.

Granted, NASA or any other space agency doesn’t have the technology to transport astronauts to and from Mars safely. Nor does it have the budget to develop the technology without cutting back on its other activities, including unmanned science missions. And even if NASA had enough money to develop a mission to Mars, the launch would be decades away.

Money and time aren’t—or shouldn’t be—a problem. At around $18 billion, NASA’s annual budget is 40% smaller than those of NIH and the Department of Energy. As for time, I think the public would understand that such an ambitious project might not be realized until the middle of the century. The great Gothic cathedrals of Europe took decades, sometimes centuries, to complete.

I would not be surprised if, sometime in the next few years, astronomers discover an Earth-like exoplanet capable of supporting life, maybe even harboring life. When they do, we humans will want to visit. In person. Getting to Mars would be a first step.