There are a lot of reasons to be excited about NASA's plan to send yet another rover to land on the Red Planet in 2020. But don't kid yourself. You wish it were a human heading to Mars instead. NASA says we have to wait until the 2030s for that to happen.

It's okay. This is a natural impulse. Way back in 1997, we saw the first Mars rover, Sojourner, land on the surface of Mars and send back some grainy images of a desolate landscape. That was exciting, because it was a new accomplishment. We put a really expensive SUV on Mars! Then, in the summer of 2004, Spirit and its sibling Opportunity landed on Mars, yielding more grainy photos of rust-colored dirt. Things got more interesting earlier this year, when Curiosity landed with a more serious arsenal of scientific instruments and started to tell us about the planet. That was exciting, because we started to learn all kinds of new things about Mars, things like evidence of flowing water on the planet's surface, the familiar make up of Martian soil and the existence of organic matter. But another rover? 

To be fair, NASA has some pretty big ambitions for the new rover, name TBD. One big part of the mission will be to actually bring some samples of Mars back to Earth, a feat that requires an unprecedented and very long flight home. Scientists also say that they're going to land the new rover in a spot that's particularly suited to preserving signs of life, if they exist. A new "science definition team" will come up with more mission objectives in the coming months. In the meantime, NASA says we should be patient. "While 2020 may seem a long way off, it's really not," said John Grunsfeld, NASA's associate administrator for science, at the announcement of the new mission. "Curiosity was about a decade in the works."

But we've seriously been waiting forever for NASA to send a man to Mars. If the Baby Boomers got to see astronauts land on the moon, plant the flag and come home to a big parade, shouldn't this generation get a space exploration event of historical proportions? The U.S. has been talking about sending a man to Mars since the 1950s, and as recently as 2004, there was an actual deadline: 2020. That deadline was pushed back, and now NASA says that we're going to go to an asteroid instead. Now, we have to wait another decade and spend billions of dollars -- $1.5 billion for this latest rover alone -- that we should've been saving up for our big manned mission to Mars.

This is where the reality check ought to kick in. Sending human beings to Mars is really hard. NASA keeps planning these interim missions in order to develop the technology and gain a better understanding of how a successful mission would be carried out on the Red Planet without killing all of the astronauts aboard. Hollywood's already taught us what can happen if things go wrong.