JOIN USNASA's Mars orbiter may have spotted remains of the pioneering Soviet Mars 3 probe - the Red Planet's first semi-successful visitor - that landed on the its surface in 1971.
Russian citizen enthusiasts found four features in a five-year-old image from Mars Reconnaissance Orbiter that resemble four pieces of hardware from the Soviet Mars 3 mission: the parachute, heat shield, terminal retrorocket and lander.
A follow-up image by the orbiter from last month shows the same features.
The Mars 3 lander transmitted for several seconds after landing on December 2, 1971, the first spacecraft to survive a Mars landing long enough to transmit anything.
"Together, this set of features and their layout on the ground provide a remarkable match to what is expected from the Mars 3 landing, but alternative explanations for the features cannot be ruled out," said High Resolution Imaging Science Experiment (HiRISE) Principal Investigator Alfred McEwen of the University of Arizona, Tucson.
"Further analysis of the data and future images to better understand the three-dimensional shapes may help to confirm this interpretation," McEwen said in a statement.
In 1971, the former Soviet Union launched the Mars 2 and Mars 3 missions to Mars. Each consisted of an orbiter plus a lander. Both orbiter missions succeeded, although the surface of Mars was obscured by a planet-encircling dust storm.
The Mars 2 lander crashed. Mars 3 became the first successful soft landing on the Red Planet, but stopped transmitting after just 14.5 seconds for unknown reasons.
HiRISE acquired a large image at this location in November 2007. This image contains 1.8 billion pixels of data, so about 2,500 typical computer screens would be needed to view the entire image at full resolution. Promising candidates for the hardware from Mars 3 were found on December 31, 2012.
An adviser to the group, Alexander Basilevsky, of Vernadsky Institute of Geochemistry and Analytical Chemistry, Moscow, contacted McEwen suggesting a follow-up image. HiRISE acquired the follow-up on March 10, 2013.
This image was targeted to cover some of the hardware candidates in colour and to get a second look with different illumination angles. Meanwhile, Russian engineers and scientists who worked on Mars 3 were contacted for more information.
The candidate parachute is the most distinctive feature in the images. It is an especially bright spot for this region, about 7.5 meters in diameter. The parachute would have a diameter of 11 meters if fully spread out over the surface, so this is consistent.