Tim Samaras, his son Paul Samaras and Carl Young died in the pursuit of science.
While tracking one of a series of tornadoes that tore through El Reno, Okla., former Discovery "Storm Chasers" Tim Samaras (pictured above), his son Paul Samaras and Carl Young died in a natural disaster that claimed six other lives.
All three men died in the pursuit of trying to learn more about tornadoes in order to improve warning systems, an effort that saves lives.
Although scientists are frequently thought of as doing dull work in white coats, the fact is that researchers like these three put their lives on the line for knowledge that would benefit all humankind.
Several of Carl Scheele's discoveries are frequently mistakenly credited to other scientists who came after him.
A pharmacist credited with identifying multiple elements for the first time, with the discovery of oxygen perhaps being his crowning achievement, Carl Wilhelm Scheele spent his life in the study of chemistry. Unfortunately for Scheele, being the first to isolate certain compounds and elements meant little was known about the dangers posed by potentially hazardous chemicals.
Scheele died as a result of the cumulative exposure to mercury, arsenic and other chemicals he kept in his pharmacy.
An early X-ray of a hand with a ring taken in the early 20th century.
Although she never completed high school, Elizabeth Fleischman Ascheim had an aptitude for the sciences that clicked once she pursued her interest in radiography. X-rays received international attention after their discovery in 1895, drawing widespread media coverage.
Fleischman became fascinated with radiophotography. She became an expert in the field within a year and opening California's first radiology lab.
Fleischman's experiments with X-rays, which would involve exposure for hours on end, would take their toll over the years, even though the potential danger of excessive, unprotected exposure had been established. She died in 1905 at age 46.
Marie Curie showed how women could contribute to and achieve in the sciences.
Marie Curie is among the most famous examples of a scientist who died in pursuit of her passion. Curie's revolutionary work on radioactivity would earn her two Nobel prizes and her achievements proved just how far she could push beyond presumed gender roles for women of her age.
The same research that brought her success as a scientist would also lead to her death. In the summer of 1934, Curie died as a result of aplastic anemia triggered by frequent, long-term exposure to radiation in her laboratory.
Apollo 1 astronauts never even made it to launch.
The first manned mission of NASA's Apollo program, AS-204, with Virgil I. "Gus" Grissom, Edward H. White II and Roger B. Chaffee, would be the first major stumble in the race to the moon.
With less than a month to go before launch, on Jan. 27, 1967, the crew died in a cabin fire that occurred during a launch pad test.
Even though the mission failed, the widows of the astronauts requested that their effort be commemorated as Apollo 1. When Apollo 11 astronauts made it to the lunar surface during their successful mission, they left behind a badge from the Apollo 1 flight crew.
David A. Johnston, taken 13 1/2 hours before the eruption of Mount St. Helens
When Mount St. Helens erupted in 1980, USGS vulcanologist David A. Johnston was the first to send out a warning letting the agency know of the disaster. Before his radio went silent, after Johnston and his trailer were overcome by the volcano blast, he relayed: "Vancouver! Vancouver! This is it!"
Though he didn't have a long life, Johnston's family, friends and co-workers all reported that he died doing what he wanted to do most: study volcanoes.
Dian Fossey's work with primates earned her the respect of fellow primatologists and the ire of poachers and tourism operators.
Dian Fossey had a dangerous job: studying gorillas in their native habitat in the forests of Rwanda. Although the primates can be aggressive, the animals themselves didn't pose any threat. Rather, Fossey's primary antagonists during her nearly two decades of study were other humans.
In 1985, Fossey was found murdered in her cabin in Virunga Mountains, Rwanda. Although an investigation and Rwanda courts came to the conclusion that Wayne McGuire, her research assistant, killed his boss, doubts about his guilt led to theories pointing to other suspects, ranging from poachers -- a frequent antagonist to Fossey's research -- and tour operators who wanted to profit from the gorillas. (McGuire was tried in absentia as he was in the United States, and never served out a prison sentence.)
The crew of the final mission of the Space Shuttle Challenger poses for a group photo.
Like the Apollo 1 astronauts before them, the crew of STS-51-L, the final mission of the Space Shuttle Challenger, was commissioned with the intention of pushing the boundaries of what's possible. For the first time in NASA's flight history, a civilian, school teacher Christa McAuliffe, with no previous flight training, would go into space.
On launch day, Jan. 28, 1986, Challenger exploded in the air 73 seconds into the flight. A defective O-ring in the space shuttle's right solid rocket booster would be to blame for the deaths of all seven crew members aboard.
Space Shuttle Columbia launches for the last time on Jan. 16, 2003.
Ten years ago, on Feb. 1, 2003, the crew of the Space Shuttle Columbia returned to Earth from what had appeared to have been a successful mission to the International Space Station. The launch of the shuttle two weeks earlier, however, caused damage to the spacecraft: A chunk of foam from the orbiter's external fuel tank broke and punched a hole in the shuttle's protective heat shield.
Upon reentry, the heat proved too much for the damaged space shuttle, which exploded in air. All seven members of the crew of STS-107 -- Rick Husband, Willie McCool, Michael Anderson, Kalpana Chawla, David Brown, Laurel Clark and Ilan Ramon -- died.
NASA, which had had a 17-year safety record since the Challenger disaster, blamed complacency for permitting the disaster to occur.
Steve Irwin died shooting what would be his final documentary. Philippe Cousteau stepped in to complete the documentary after Irwin's death.
Steve Irwin, also known as the Crocodile Hunter, was an animal lover, an educator and an entertainer. On a shoot for a documentary on Batt Reef in Queensland, Australia, on Sept. 4, 2006, Irwin was struck in the chest by a stingray. The animal's barb pierced his heart, and he died from his injuries.
His wife, Terri, carries on the couple's work in her role as the owner of the Australia Zoo.