Dhaka, May 3 -- A Soviet-era spacecraft meant to land on Venus in the 1970s is expected to soon plunge uncontrolled back to Earth.It's too early to know where the half-ton mass of metal might come down or how much of it will survive reentry, according to space debris-tracking experts.Dutch scientist Marco Langbroek predicts the failed spacecraft will reenter around May 10. He estimates it will come crashing in at 150 mph (242 kph), if it remains intact."While not without risk, we should not be too worried," Langbroek said in an email.The object is relatively small and, even if it doesn't break apart, "the risk is similar to that of a random meteorite fall, several of which happen each year. You run a bigger risk of getting hit by lightning ...