Also a so-called "juvenile" SF novel by Jack Williamson, published in 1968. The story tells of a rescue mission to the star Topaz. Astronaut Ben Stone and his crew are lost, and a rescue team featuring his young brother Jeff Stone is assembled. Jeff takes command when the pilot is injured. He must solve the mystery of the missing mission and the alien "rock hoppers" in Topaz's asteroid belt.

This was one of the first SF books I read "all by myself" and a childhood favourite. I'm fortunate to have a copy rescued from the library's discard sale. Like most of Williamson's work it has borne up decently over the years and is still a good, if quick, read today. Still in print as a Scholastic paperback ... recommended!