TOKYO (AP) — Japanese space experts say they will examine soil samples brought back from a distant asteroid in an attempt to find the source of heat that altered the celestial body, in their search for clues to the origin of the solar system and life on Earth. Scientists at the Japan Aerospace Exploration Agency say they have made a preliminary examination of 5.4 grams (0.19 ounce) of soil which the Hayabusa2 spacecraft brought back in December from the asteroid Ryugu, more than 300 million kilometers (190 million miles) from Earth. The scientists say the asteroid was exposed billions of years ago to extremely high temperatures, possibly caused by an internal source of heat or planetary collisions rather than heat from the sun.