NASA centers across the nation invite journalists and the public to see and hear about the agency's efforts and contributions to understanding and protecting Earth.

Begun in 1970, Earth Day is the annual celebration of the environment and a time to assess work still needed to protect the natural resources of our planet. The agency maintains the largest contingent of dedicated Earth scientists and engineers in leading and assisting other agencies in preserving the planet's environment.

For a comprehensive listing of NASA Earth Day activities, visit: http://www.nasa.gov/earthday

The Web site also features an online poll inviting the public to vote for the most important contribution NASA has made to exploring Earth and improving the way we live on our home planet. The "greatest hits" poll closes April 21. A new interactive feature will debut on Earth Day, April 22, that allows visitors to view a collection of astronaut photographs of Earth as seen from the current location of the International Space Station.

Please note all times are local. NASA center events include:

NASA Headquarters, Washington
Sunday, April 19 (12 - 7 p.m. EDT) - NASA is participating in the Earth Day Celebration at the National Mall with an exhibit on a wide range of environmental issues as seen from space, including air pollution, urban development, hurricanes, and dust storms. Visitors to the booth will be able to meet NASA Earth scientists and see NASA satellite images of Earth.

Wednesday, April 22 (1 p.m. EDT) - In honor of Earth Day and the 40th Anniversary of the Apollo program, NASA will take part in an event at the National Arboretum in Washington to plant a moon sycamore tree. The tree was grown from a second-generation seed from seeds flown to the moon and returned to Earth by the crew of Apollo 14 in 1971.

Ames Research Center at Moffet Field, Calif.
Tuesday, April 21 (9 a.m. - 4 p.m. PDT) - A technology expo sponsored by the NASA Research Park and the NASA Ames Innovative Partnerships Program will showcase technologies related to exploration and sustainability. More than 40 exhibits will be on display underscoring NASA's vision of leveraging technology for a cleaner, greener Earth.

Dryden Flight Research Center, Edwards, Calif.
Tuesday, April 21 (10 a.m. - 2 p.m. PDT) - View a model of the unmanned Ikhana aircraft. Ikhana was instrumental in assisting emergency response efforts during recent California wildfires. The public also will see high-altitude life-support demonstrations and can attend several educational activities and presentations.

Glenn Research Center in Cleveland
Sunday, April 19 (10 a.m. - 5 p.m. EDT) - A variety of educational displays will be at the Cleveland Metro Park Zoo.

Goddard Space Flight Center in Greenbelt, Md.
Wednesday, April 22 (10 a.m. and 2 p.m. EDT) - NASA Goddard Digital Learning Network presents two webcasts for students and teachers of "Bella Gaia" (Beautiful Earth), a unique multimedia journey of Earth from space by director and violinist Kenji Williams. The performance will be broadcast live. For more information, visit http://dln.nasa.gov .

Jet Propulsion Laboratory in Pasadena, Calif.
Saturday, April 25 and Sunday, April 26 (9 a.m. - 5 p.m. PDT) - JPL will join a celebration of our ocean planet at the ninth annual Earth Day event at the Aquarium of the Pacific in Long Beach, Calif. The event will include exhibits and handouts highlighting NASA's Earth science research.

Kennedy Space Center, Fla.
Wednesday, April 22 (10 a.m. - 3 p.m. EDT) - Local and county government officials will showcase their environmental activities. Topics will include natural resources, energy conservation, recycling, alternative fuel vehicles and environmentally friendly products.

Langley Research Center in Hampton, Va.
Saturday, April 18 (1 p.m. EDT) - Presentation on "Looking at Earth from Space" at the Virginia Zoo's "Party for the Planet: Earth Day at the Zoo."

Tuesday, April 21 (7 p.m. EDT) - Lecture on "Satellite Observations of Air Pollution: Local Impacts Seen from a Global Perspective" at Thomas Nelson Community College's Espada Conference Center in Hampton.

Marshall Space Flight Center in Huntsville, Ala.
Tuesday, April 21 (10 a.m. - 12:30 p.m. CDT) - The theme of Marshall's Earth Day event for employees and contractors is water stewardship, with the slogan "Just one drop, priceless." A taste test is planned using water recycled through the Environmental Control and Life Support System used on the International Space Station. A vendor fair will be held highlighting environmentally friendly products. Special guests include local area mayors.

Stennis Space Center near Bay St. Louis, Miss.
Wednesday, April 22 (10 a.m. - 2 p.m. CDT) - Energy awareness displays and a video presentation highlighting the "green building" aspects of the center's new Emergency Operations Center. Activities also will feature raffles, environmentally focused games, cell phone recycling and other environment-friendly exercises.

Wallops Flight Research Facility on Wallops Island, Va.
Saturday, April 18 (10 a.m. - 4 p.m. EDT) - Several events will be held in collaboration with the Salisbury Zoo. The theme "Rockets and Critters" focuses on protecting threatened and endangered species while operating a NASA launch range.

For information about the NASA and agency activities, visit: http://www.nasa.gov