London: NASA has finally started revealing the secrets it hid in engineers in the Curiosity rover, which is currently driving on the surface of Mars.
Engineers at the space agency have admitted that they used special coded tyre tracks on the rover.
They use morse code to spell out JPL (Jet Propulsion Lab), the lab where the rover was put together.
The track pattern - dot-dash-dash-dash, dot-dash-dash-dot, dot-dash-dot-dot ('.--- .--. .-..') - spells out 'JPL' in Morse code, which translates letters and numbers into a series of short ("dot") and long ("dash") signals.
"We have intentionally put holes in the wheels to leave a unique track on Mars," the Daily Mail quoted lead rover planner Matthew Heverly, of NASA's Jet Propulsion Laboratory in Pasadena, as saying.
"So if we are in sand dunes where we don't have lots of rock features around us, we can use those patterns to do our visual odometry," he said,
In addition to the Morse code JPL, Curiosity's wheels also feature a zigzag cleat pattern.
Codes on the rover will be used by a smartphone app.
The includes a code on the rover that, at some point in the future, NASA will be using a special smartphone app to give space fans information.
However, it has so far refused to give any more information on the codes, other than saying the tags will "allow the public to have an immersive experience of discovery as it happens".
Fiduciary marks on the rover are used to checks its parts haven't moved. Several are dotted over its surface, looking like small targets.
The rover's cameras image the small icons - which look like circles sliced into quarters - before and after a move.
This way, engineers can compare how much Curiosity's arm has shifted to the left or how far its wrist has twisted clockwise.
They can they use the data to build a 3-D dataset of all the rover's moving pieces.
Curiosity also carries a Martian sundial so that operators can keep track of the sun's position and even that has a hidden message, saying 'TO MARS TO EXPLORE'
Curiosity's sundial has the word for Mars written in 16 languages on it.
It is also used to calibrate Curiosity's high-resolution 3-D color MastCams with red, blue, yellow, and green bands on the sundial help the cameras attune to their surroundings.
The sundial also carries an inscription that will serve as a monument once the rover has finally ended its mission.
"To Mars, To Explore," it reads.
"For millennia, Mars has stimulated our imaginations. First, we saw Mars as a wandering star, a bringer of war from the abode of the gods. In recent centuries, the planet's changing appearance in telescopes caused us to think that Mars had a climate like the Earth's. Our first space age views revealed only a cratered, Moon-like world, but later missions showed that Mars once had abundant liquid water.
"Through it all, we have wondered: Has there been life on Mars? To those taking the next steps to find out, we wish a safe journey and the joy of discovery," it reads.
A tiny chip on the rover carries the names of 1.24 million people who signed up via Nasa's website
A lucky penny is used to calibrate Curiosity's camera system, and Curiosity is also said to be carrying cash.