An advanced mini-robot named Tlaloc II-TC discovered three chambers built under the Temple of Quetzalcoatl, in the ancient city of Teotihuacan, built approximately 2,000 years ago in the northeast of what now is Mexico City.
Mexican archaeologists used the robot to access the last section of a very narrow tunnel under of the temple. The team, directed by Sergio Gómez Chávez, found multiple chambers instead of one, as it was expected, the National Institute of Anthropology and History (INAH) in Mexico said.
Tláloc II-TC is a system of three independent mechanisms. The main one is a transport vehicle that weights about 35 kilograms (77 pounds) and is approximately 45 cm tall. It features a scanner that can map its surroundings within a 5-meter radius.
"The images registered with the video camera and the scanner were precise. The upper part of the tunnel is a semicircle and it stays constant up to the entrance of the chambers. It appears they are divided by a wall or a huge stone," Gómez Chávez said in a statement in an INAH bulletin. "Also, they have a depth of more than 5 meters. We know this because that's the maximum measurement that the scanner can register, and it was indicating more depth."
The second part of the system is an insect robot that is transported by the main vehicle. It's 40 centimeters long and it has an infrared camera. Its advantage is that it can explore further and avoid some obstacles.
The last part of the system is a helicopter with a video recorder. Gómez Chávez explained this last one is not used in interiors because of the risk that the underground air currents pose to it.
One of the main obstacles the robot found was the amount of mud in the tunnel, which in some parts went up to 30 centimeters (7 to 11 inches) deep.
Despite this, the engineer Hugo Armando Guerra of HA Robotics and his colleagues Francisco Castañón and Alberto Álvarez, said that the robot had a "successful" trip in the 65 feet of muddy conditions that it traveled.
The robot has inspected approximately 76 meters (249 feet) of the tunnel, which in total is about 120 meters long (393 feet), according to the INAH.
In 2010, a robot named Djedi explored the Cheops pyramid in Egypt. Doctor Ng Tze Chuen, who created that robot, is helping the HA Robotics and INAH team with the modifications made to the Tlaloc II-TC for this mission, called Tlalocan: Underground Road.
"In the Great Pyramid (Cheops), Djedi went through a narrow and steep tunnel and it just corroborated the presence of a wall. Without any doubts, in Teotihuacan there will be important findings," said Tze Chuen.
"Both buildings (Cheops and the Temple of Quetzalcoatl) are absolutely different, both in their construction, and in their antiquity. The first one is 4,000 years old and the second one 2,000 years old. However, here (in the Temple of Quetzalcoatl) there is more space to explore," said Tze Chuen, according to the INAH.
The temple was built approximately 2,000 years ago in honor of the god Quetzalcoatl, the Feathered Serpent.
"Now we know that there are three chambers," Gómez said. "The next step is to take the pertinent measures to remove the sediments and the filling that was placed by the Teotihuacans to block the last stretch of the tunnel."
The archaeologists believe that in the last part of the tunnel, they will find a staircase that descends about 4 meters into an underground gallery that might be 10 meters long.