UFO enthusiasts have spotted a "cigar-shaped" UFO orbiting the planet Mars, while looking through photographs taken by Nasa's Curiosity Rover earlier this month.

Curiosity has been exploring the Gale Crater on Mars since 2012, tasked with the mission of investigating the Martian climate and geology to assess whether a selected field site inside Gale Crater can offer environmental conditions suitable for microbial life.

Raw images are taken by the Mars Rover during its explorations based on commands issued by the mission team. There are a total of 147,901 images uploaded onto Nasa's Mars Science Laboratory website, and these images can only be relayed back to Earth when orbiters pass over the Rover.

On 4 May, the Rover's right-hand side navigation camera picked up a long, thin white object hovering in the air for about 16 minutes.

According to UFO Sightings Daily blogger Scott Waring, a teacher living in Taiwan who has authored a few books on UFOs, time-travel and young adult fantasy fiction, the UFO is the same one that was captured on camera by Curiosity on 28 April.

"NASA photos used to have high detailed descriptions, but not these rover photos. NASA tries not to give a lot of details in case a photo surfaces with something they cannot and will not explain, like these six images, five having a UFO in them," he writes in a blog post.

"I took the photos and enlarged them from 3kb size to 19kb size in order to show the true detail of the photo. I am not a NASA scientist and should not have to do this.

"They get photos from the rover that are always 1MB at the smallest and upwards of 600MB in size in HD detail, so why does NASA put up these tiny images for the public to view, when they have such massive sized originals? It shows NASA's obliviousness to the needs of the people."

User UFOvni2012 on YouTube has also spotted the UFO captured by Mars, and created a video putting Nasa's images together, that shows the unidentified object landing in the Gale Crater and flying through the air.

The video also points out UFOs behind the cigar-shaped object moving through the atmosphere as well.

Could the objects in the Nasa photos be the Mars Reconnaissance Orbiter satellite that orbits Mars to pick up data from the Curiosity Rover, or a UFO?

Would-be space explorers can view a wide range of Mars images taken by both the Orbiter and the Curiosity Rover in the Multimedia section of Nasa's Mars website.