Overall, its exploration history is similar to those of Mars and of Phobos.
Deimos has been photographed in close-up by several spacecraft whose primary mission has been to photograph Mars.
No landings on Deimos have been made.

The Soviet Phobos program sent two probes to Phobos.
In case Phobos 1 succeeded, Phobos 2 could have been sent to Deimos.
Both probes launched successfully in July 1988.
The first was lost en route to Mars, whereas the second returned some data and images but failed shortly before beginning its detailed examination of Phobos's surface, including a lander.

In 1997 and 1998, the proposed Aladdin mission was selected as a finalist in the NASA Discovery Program.
The plan was to visit both Phobos and Deimos, and launch projectiles at the satellites.
The probe would collect the ejecta as it performed a slow flyby (~1 km/s).
These samples would be returned to Earth for study three years later.
The principal investigator was Carle M. Pieters of Brown University.
The total mission cost, including launch vehicle and operations was $247.7 million.
Ultimately, the mission chosen to fly was MESSENGER, a probe to the planet Mercury.

In 2008, NASA Glenn Research Center began studying a Phobos and Deimos sample-return mission that would use solar electric propulsion.
The study gave rise to the "Hall" mission concept, a New Frontiers-class mission currently under further study.

Also, the sample-return mission called Gulliver has been conceptualized and dedicated to Deimos, in which 1 kilogram (2.2 pounds) of material from Deimos would be returned to Earth.

Another concept of sample-return mission from Phobos and Deimos is OSIRIS-REx 2, which would use heritage from the first OSIRIS-REx.

In March 2014, a Discovery class mission was proposed to place an orbiter on Mars orbit by 2021 and study Phobos and Deimos.
It is called Phobos And Deimos & Mars Environment (PADME).

Human exploration of Deimos could serve as a catalyst for the human exploration of Mars.
Recently,  it was proposed that the sands of Deimos or Phobos could serve as a valuable material for aerobraking in the colonization of Mars.
Because the small delta-v budget of Phobos, a small amount of chemical fuel brought from Earth could be transformed in a very large amount of sand lifted from the surface of Phobos –  from a permanent outpost, to a transfer orbit.
This sand could be released in front of the spacecraft during the descent maneuver and then resulting in a densification of the atmosphere just in front of the spacecraft.
Overall, its exploration history is similar to those of Mars and of Phobos. Deimos has been photographed in close-up by several spacecraft whose primary mission has been to photograph Mars. No landings on Deimos have been made.
The Soviet Phobos program sent two probes to Phobos. In case Phobos 1 succeeded, Phobos 2 could have been sent to Deimos. Both probes launched successfully in July 1988. The first was lost en route to Mars, whereas the second returned some data and images but failed shortly before beginning its detailed examination of Phobos's surface, including a lander.
In 1997 and 1998, the proposed Aladdin mission was selected as a finalist in the NASA Discovery Program. The plan was to visit both Phobos and Deimos, and launch projectiles at the satellites. The probe would collect the ejecta as it performed a slow flyby (~1 km/s). These samples would be returned to Earth for study three years later. The principal investigator was Carle M. Pieters of Brown University. The total mission cost, including launch vehicle and operations was $247.7 million. Ultimately, the mission chosen to fly was MESSENGER, a probe to the planet Mercury.
In 2008, NASA Glenn Research Center began studying a Phobos and Deimos sample-return mission that would use solar electric propulsion. The study gave rise to the "Hall" mission concept, a New Frontiers-class mission currently under further study.
Also, the sample-return mission called Gulliver has been conceptualized and dedicated to Deimos, in which 1 kilogram (2.2 pounds) of material from Deimos would be returned to Earth.
Another concept of sample-return mission from Phobos and Deimos is OSIRIS-REx 2, which would use heritage from the first OSIRIS-REx.
In March 2014, a Discovery class mission was proposed to place an orbiter on Mars orbit by 2021 and study Phobos and Deimos. It is called Phobos And Deimos & Mars Environment (PADME).
Human exploration of Deimos could serve as a catalyst for the human exploration of Mars. Recently,  it was proposed that the sands of Deimos or Phobos could serve as a valuable material for aerobraking in the colonization of Mars. Because the small delta-v budget of Phobos, a small amount of chemical fuel brought from Earth could be transformed in a very large amount of sand lifted from the surface of Phobos –  from a permanent outpost, to a transfer orbit. This sand could be released in front of the spacecraft during the descent maneuver and then resulting in a densification of the atmosphere just in front of the spacecraft.
Deimos (moon)