Our best chance to send humans to Mars will be in the mid-2030s, but the Red Planet might not be our final destination. It might actually be much easier and just as effective to land on Mars's moon tiny Deimos.
That's the plan put forward by Lockheed Martin's Project Red Rocks, which suggests Deimos would be a useful intermediary step before attempting to land on Mars itself. They point out that we can land on Deimos using pretty much the exact same technology we used to put the Apollo craft on the Moon, sidestepping the massive challenge of escaping Mars's far greater gravity.
The best windows for trips to Mars will be in 2033 and 2035. Not only will the relative positions of Earth and Mars allow us to keep propulsion costs down, the Sun's magnetic field will be particularly strong at those times, offering astronauts a natural shield from cosmic radiation. One plan then would be to send equipment and supplies ahead in a probe in January 2031, then send astronauts to Deimos in 2033. They would then spend 18 months orbiting Mars before returning by November 2035.
According to the Lockheed Martin engineers who came up with Project Red Rocks, a Deimos landing offers a lot of benefits. There's a spot in the northernmost regions of the moon that enjoys continuous sunlight for ten straight months, which would allow the mission to harness simple solar energy systems. During the Martian winter, they could then shift to a similar spot in the southern hemisphere.
Being on Deimos wouldn't cut the astronauts off from Mars completely. They could still control rovers much like we do now, but the fact that they would only be several thousand miles away instead of many millions of miles would give them much finer control and cut out the time delay imposed by the speed of light. Deimos would also be useful as it's a natural middle ground where astronauts could quarantine and examine samples brought up from Mars without risking contamination back on Earth.
The Lockheed Martin fact sheet also argues:
"Sending astronauts to Deimos will demonstrate key technologies that will be needed for subsequent human Mars landings, such as reliable life-support recycling systems, long-term cryogenic propellant storage, and the biomedical technology to protect astronauts from the effects of microgravity and space radiation. [This mission would be more affordable] because it postpones the development of difficult technologies needed only for Mars landings, such as nuclear power, lightweight space suits, biological containment to prevent interplanetary contamination, and advanced re-entry systems for landing large spacecraft."
The Deimos mission could accomplish a very healthy percentage of what we want out of a Mars mission - except for the huge psychological component of actually being able to say we landed on another planet, of course - all without requiring massive upgrades to our existing technologies. Lockheed Martin engineer Josh Hopkins explains:
"Each mission is designed to incrementally build up capabilities for the next mission and address scientific questions about a common theme: the origins and formation of our solar system. The Red Rocks mission builds on each of those prior missions, and it, in turn, lays the groundwork for an eventual human landing on Mars. There are things required for the interplanetary trip in space from Earth to Mars and back, and then there are the challenges specific to actually landing and operating on Mars itself. A trip to Deimos is very similar to the in-space parts of a trip to Mars in terms of distance, duration, and environment."
Deimos and its companion moon Phobos are also of interest to researchers beyond their role as natural space stations for Mars explorers. They're tiny, irregular objects, nothing like our own Moon, and we still don't have a good handle on exactly what they are or how they formed. While a mission to Deimos lacks some of the raw grandeur of actually landing on Mars, it might actually offer even more exciting opportunities than a mission to the Red Planet itself.