HOUSTON --Friday was a somber anniversary for the space program -- the space shuttle Challenger exploded 25 years ago today. There were memorial services at Kennedy and Johnson Space Centers to mark the moment, and also a number of events all day long at the Challenger Learning Center at the Houston Museum of Natural Science. On this day in 1986, the Challenger exploded into pieces on live television. It happened just 73 seconds into the flight. There was no escape system and the seven crew members died in that accident. A tribute was held this morning to the Challenger crew at the Kennedy Space Center in Florida and included a speech from a widow of one of the Challenger astronauts. June Scobee Rodgers, widow of flight commander Dick Scobee, helped establish the Challenger Center for Space Science Education. There are now dozens of those educational centers around the nation, including here in Houston. The center in Houston was the first. Today, the Challenger Foundation opened its 48th center -- not to remember the day 25 years ago or in particular the seven brave Americans who died -- but to make sure that someone comes after them to continue the mission. The dream of space as a classroom is still alive today. Inside the Challenger Learning Center at the Houston Museum of Natural Science, students study space science and practice teamwork in mock missions. "Just learning how to work together come make scientific facts come true," said Sebastian Perez, a local 5th grade student. The centers - now 48 all across the country - came about because the families of those lost in the Challenger accident 25 years ago today pushed for them. "This is a typical example of triumph over tragedy," said Gerry Griffin, former Director of Johnson Space Center. Learning was so closely tied to the Challenger mission. Christa McAuliffe was going to be the first teacher in space, giving lessons from an orbiting classroom. "I am so excited to be here today. I hope everyone tunes in on day four to see the teacher teach from space," McAuliffe said back in January 1986. And it was the reason so many kids were watching that day. The reason an entire generation of 30-somethings now know the next scene without even having to see it. A teacher and her six brave colleagues lost 25 years ago today, but not forgotten in the minds of kids and parents today who still can see space as a classroom, and seven brave astronauts as teachers. "I think to a person all of them would say, 'Don't let this stop. Let's press on,'" Griffin said. Of course, all of this is happening with just three shuttle flights left. Dick Scobee's widow told us today though she is confident the kids who go through the center will build the vehicle to take us to Mars. This week is a tough one every year for NASA. Tuesday will mark eight years since the Columbia disaster. Seven astronauts died on that doomed flight when the shuttle broke apart on re-entry over east Texas. Yesterday was the 44th anniversary of the day the Apollo 1 command module caught fire on the launch pad. Three astronauts died in that disaster.