A new study shows that astronauts on the Apollo mission, who were exposed to deep-space radiation, may have suffered greater health risk to their hearts than other space travelers. The astronauts on that trip to the moon, in both the 1960s and 1970s, are the only ones who have flown past the magnetic shielding of the Earth. The study found an increased number of deaths caused by cardiovascular problems in the astronauts who encountered deep-space. Michael Delp, the lead author of the study, said, "With deep-space radiation, really, the 24 Apollo astronauts that went to the moon are the only astronauts that have really been exposed to this, because all the others—cosmonauts and astronauts—have stayed in low-Earth orbit." He added, "This was really the first indication that travel into deep space might have some health consequences, particularly on the cardiovascular system."