Because the vast distance is only one of the many obstacles that complicate a trip to Mars, the odds of actually getting something there in working condition aren’t anything you’d accept when booking your next flight to Rhode Island or New Hampshire. Since the first attempt in 1960, only 19 of 45 missions to Mars—just over 40 percent—have been complete successes.

Even after more than a half-century of experience and technological development, every mission to land on Mars is still a one-of-a-kind gamble. Today, with all our knowledge, this complexity and difficulty mean it costs around $1.5 million in shipping and handling for every pound of robotics and instrumentation you want to send to the Martian surface.

That is why it is so heroically challenging to touch and do things on another world. As of right now, there is no such thing as “just sending stuff to Mars.” That may change someday, but today it takes billions of dollars, thousands of engineers and scientists, and decades of experience to so much as dig a hole on Mars, a task anyone on Earth can do with five minutes and a five-pound shovel (which would run you a cool $7.5 million just to ship to the red planet). Mars is our astronomical next-door neighbor—it’s about as easy a trip as we can take—but our ability to interact with it is just barely this side of nonexistent.

Passive observation, looking up in the sky, has been the only option for interacting with Mars for almost all of human history. Over the last 400 years, we’ve been eyeballing the planet with increasingly powerful telescopes, but there are limits to what you can learn about a place with passive observation alone. (You would need a telescope with a primary mirror bigger than South Carolina to look at individual pebbles on Mars.) So, starting in 1965, we sent cameras out to Mars orbit, then had them snap photos and transmit them back.

But if you’re willing to go the all the way down the Martian gravity well and touch down on the surface with a lander or rover, the range of scientific possibilities explodes. Humans did this successfully for the first time in 1976, with the Viking missions. Landers and rovers can physically interact with their environment and do exciting new things like flip a rock over to see what’s on the other side, scrape away the top surface of a rock to see what it looks like inside, or drill holes into the ground. Scientists can then deploy instruments, like the X-ray diffraction instrument on the Curiosity rover (used to observe crystalline structure in rocks), that need to be right next to a target to work.



The tricky part here is that science continually generates bigger and more complex questions; solve one riddle, and you end up with two new ones. Anyone who has found themselves intellectually run aground by a 4-year-old repeatedly asking “Why?” has experienced this phenomenon firsthand. Over time, answering those questions requires ever-increasing scientific firepower.



Even on Earth, hunting for signs of life from billions of years ago isn’t easy and requires both field investigation and detailed analysis in the laboratory. There’s only so much you can do at the scene of the investigation; eventually, you need to send samples back to the lab for further analysis. We are now getting to the point where we’re asking the kinds of questions about Mars that we can’t answer with fieldwork alone.



Broadly speaking, scientists want to bring back Mars samples to address three different sets of questions: geological, biological, and technological. Geologists want to understand, in detail, the history of Mars and see what conditions have prevailed there over the last few billion years. Biologists want to figure out if those conditions gave rise to life. The technologists want samples so they can figure out the details, feasibility, and risks of sending humans there someday.



As challenging as a round trip to Mars is, it makes more sense as a way to answer today’s scientific questions than sending the lab equipment to Mars. For example, geologists would love to send an ion microprobe that can measure elemental abundances at the scale of millionths of a meter; the abundances of particular isotopes can then be used to determine the age of a specific bit of rock in a sample. But those machines are big and power-hungry. Shrinking one down to size and getting it to Mars would be a costly engineering project you’d need to manage before even looking at your first Mars sample. But even if you manage to make it lean and portable, room for science payloads is zero-sum. Adding an ion microprobe means taking off something else.



Further, anything you can send is sharply limited in capability. The enormous cost of shipping instruments not only restricts what you can send to Mars, but it also puts a considerable squeeze on their power and mass, bounding their precision and capabilities.



The limitations on precision and delicacy go beyond the instruments to the handling of the samples themselves.



The immense distance to Mars means the fastest the speed of light will let you send a signal to Earth to Mars and back again is just over six minutes round trip (in the worst-case scenario, that roundtrip time for a signal climbs to almost 45 minutes). That means there’s an enormous lag between telling your robot to do something, seeing if it worked, and then telling it to go the next step. The time needed to do something, observe the results, decide what to do, and then act is critical. Doing anything with up to a 40-minute lag is an exercise in patience and a recipe for missed opportunities.



Compare this with human reaction times of about a quarter second. In an eight-hour shift, a person on Earth is limited—at absolute theoretical maximum—to about 78 round trip communications with something on the surface of Mars. If you bring that sample back to Earth, the time needed to send a signal back and forth to an instrument drops to nearly zero. A scientist in the lab could (in theory) complete tens of thousands of interactions with a sample in the same eight hours. Once you can handle and interact with a sample continuously, it allows you to do all kinds of new science, like looking for extraordinarily small things like fossils of ancient microbes, imprints of mold spores, and trails left by stone-eating bacteria. In the lab, investigators can pick apart rocks with incredible care and precision.



Scientists have been thinking for decades about the kinds of experiments they could do once they have samples back on Earth. Indeed, the most recent report, “The Potential Science and Engineering Value of Samples Delivered to Earth by Mars Sample Return,” says “Potential [signs of life on Mars] can be investigated thoroughly only by observation-guided sample preparation, followed by investigations by laboratory consortia that apply state-of-the-art techniques.”



The change in both how samples can be processed, and the tools used to examine them will be huge. Let’s just take one example out of hundreds or thousands. In theory, it might not only be possible to find impressions left by hypothetical Martian mold spores in ancient rocks but also to immediately test the sedimentary rock to determine how long ago those spores landed in Mars mud. And all that could be done in the space of days or weeks.



The ability to do all that “observation-guided sample preparation followed by investigations” would be such a huge breakthrough that the scientific value of going even from zero Martian soil to a little Martian soil is effectively immeasurable. Not so the price tag; MSR will cost at least $7 billion.



This graduation from sending information back to Earth to sending actual Martian stuff back to Earth involves fundamental changes in the way we think about space exploration. Up to now, we’ve been able to go to Mars and choose among a whole world of different samples—but we could only do so much with them. With MSR, it’ll be the opposite.