Question: When were the astronauts for the first manned space program of the United States announced? 

Context paragraphs:
Mercury Seven: The Mercury Seven were the group of seven Mercury astronauts announced by NASA on April 9, 1959.  They are also referred to as the Original Seven or Astronaut Group 1.  They piloted the manned spaceflights of the Mercury program from May 1961 to May 1963.  These seven original American astronauts were Scott Carpenter, Gordon Cooper, John Glenn, Gus Grissom, Wally Schirra, Alan Shepard, and Deke Slayton.

Gordon Cooper: Leroy Gordon "Gordo" Cooper Jr. (March 6, 1927 – October 4, 2004), (Col, USAF), better known as Gordon Cooper, was an American aerospace engineer, test pilot, United States Air Force pilot, and one of the seven original astronauts in Project Mercury, the first manned space program of the United States.

Neutral Buoyancy Simulator: The Neutral Buoyancy Simulator was a neutral buoyancy pool located at NASA's George C. Marshall Space Flight Center (MSFC).  Engineers and astronauts developed hardware and practiced procedures in this tank from its completion in 1968 through its decommissioning in 1997.  Marshall recognized the need for underwater simulations of extra-vehicular activities (EVAs) and developed three successively larger tanks for the purpose.  The Neutral Buoyancy Simulator contributed significantly to the American manned space program.  Skylab, the Space Shuttle, Hubble Space Telescope, and the International Space Station have all benefited from the Neutral Buoyancy Simulator.  Until Johnson Space Center constructed the Weightless Environment Test Facility in the mid-1970s, MSFC had the only NASA-owned test facility that allowed engineers and astronauts to become familiar with the dynamics of body motion under weightless conditions.

First Landing: First Landing is a 2002 science fiction novel by Robert Zubrin that tells the story of the first manned space expedition to Mars.  Zubrin is the head of the Mars Society, an organization lobbying the real world NASA to send astronauts to Mars.  The plan used to accomplish their mission in the book is the same one advocated by his group.

1986 in spaceflight: The year 1986 saw the destruction of Space Shuttle Challenger shortly after lift-off, killing all seven aboard, the first in-flight deaths of American astronauts.  This accident followed the successful flight of Columbia just weeks earlier, and dealt a major setback to the U.S. manned space program, suspending the Shuttle program for 32 months.

Mercury-Atlas 7: Mercury-Atlas 7, launched May 24, 1962, was the fourth flight of Project Mercury, the first manned space program of the United States.  The Mercury spacecraft, named Aurora 7, made three Earth orbits, piloted by astronaut Scott Carpenter.  He was the sixth human and the fourth American in space.

Jay Barbree: Jay Barbree (born November 26, 1933) is a correspondent for NBC News, focusing on space travel.  Barbree is the only journalist to have covered every manned space mission in the United States, beginning with the first American in space, Alan Shepard aboard "Freedom 7" in 1961, continuing through to the last mission of the Space Shuttle, "Atlantis's" STS-135 mission in July 2011.  Barbree has been present for all 135 space shuttle launches, and every manned launch for the Mercury, Gemini, and Apollo eras.  In total, Barbree has been witness to 166 manned space launches.

Soyuz 9: Soyuz 9 (Russian: Союз 9 , "Union 9") was a 1970 Soviet manned space flight.  The two-man crew of Andrian Nikolayev and Vitali Sevastyanov broke the five-year-old space endurance record held by Gemini 7, with their nearly 18-day flight.  The mission paved the way for the Salyut space station missions, investigating the effects of long-term weightlessness on crew, and evaluating the work that the cosmonauts could do in orbit, individually and as a team.  It was also the last flight of the first-generation Soyuz 7K-OK spacecraft, as well as the first manned space launch to be conducted at night.  To date, Soyuz 9 marks the longest manned flight by a solo spacecraft.

Gemini 3: Gemini 3 was the first manned mission in NASA's Gemini program, the second American manned space program.  On March 23, 1965, astronauts Gus Grissom and John Young flew three low Earth orbits in their spacecraft, which they nicknamed Molly Brown.  This was the ninth manned US spaceflight (including two X-15 flights over 100 kilometers), and the 17th world human spaceflight including eight Soviet flights.  It was also the final manned flight controlled from Cape Kennedy Air Force Station in Florida, before mission control functions were shifted to a new control center located at the newly opened Manned Spacecraft Center in Houston, Texas.

Shenzhou 10: Shenzhou 10 () was a manned spaceflight of China's Shenzhou program that was launched on 11 June 2013.  It was China's fifth manned space mission.  The mission had a crew of three astronauts: Nie Haisheng, who was mission commander and previously flew on Shenzhou 6; Zhang Xiaoguang, a former PLAAF squadron commander who conducted the rendezvous and docking; and Wang Yaping, the second Chinese female astronaut.  The Shenzhou spacecraft docked with the Tiangong-1 trial space laboratory module on 13 June, and the astronauts performed physical, technological, and scientific experiments while on board.  Shenzhou 10 was the final mission to Tiangong 1 in this portion of the Tiangong program.  On 26 June 2013, after a series of successful docking tests, Shenzhou 10 returned to Earth.

Supporting paragraphs: Mercury Seven Gordon Cooper
Answer: April 9, 1959