Japan's space probe Hayabusa2 started its descent to an asteroid 340 million kilometers from Earth on Thursday on its mission to provide insight into the evolution of the solar system and the origin of life.

The spacecraft started its descent at 1 p.m. Japan Time after a delay of a few hours caused while the final landing procedure was confirmed. The probe's condition is normal, the Japan Aerospace Exploration Agency said, and it is expected to touch down as scheduled on Friday morning to collect samples from the rocky surface.

Hayabusa2 arrived near the Ryugu asteroid in June after traveling 3.2 billion kilometers on an elliptical orbit around the sun for more than three years. Its landing area is six meters in diameter, which although flat, is surrounded by large rocky formations and necessitates precise control of the probe.

[Image courtesy of JAXA]

The touchdown was originally planned for last October but was postponed after the asteroid's surface was discovered to be rougher than initially thought, requiring time to find a good landing site.

Ryugu, with an estimated diameter of about 900 meters, travels around the Sun once every 16 months, passing near the orbits of Earth and Mars.

Hayabusa2, launched from Tanegashima Space Center in southwestern Japan in 2014, is due to return to Earth at the end of 2020 after making three landings on the asteroid, which is believed to contain water and other materials for life.

The spacecraft will fire a small projectile when the tip of a cylinder-shaped horn protruding from its body touches Ryugu's surface, making an artificial crater and capture unexposed materials.

The first Hayabusa asteroid probe launched in 2003 returned to Earth in 2010 after obtaining the first ever samples from an asteroid.

Hayabusa, meaning falcon in Japanese, landed twice on the asteroid Itokawa about 300 million kilometers from Earth, having survived a series of technological problems. It failed to deploy its trajectory but managed to return with some asteroid particles that were caught up on the probe when it touched down on the surface.