Prof. Donald Brownlee expects to find in the dust brought by the spacecraft evidence of the formation of the solar system, and perhaps even of the birth of the universe itself
For 20 years Prof. Donald Brownlee of the University of Washington has been trying to send a spacecraft to meet a comet, and even return. In 1980, he began collecting cosmic dust particles called "Brownian particles" after him. He sought to thoroughly study Halley's comet, but was unable to bring samples from it to Earth. Now with the help of NASA's Jet Propulsion Laboratory and Lockheed-Martin Astronautics it is possible for his dream to come true.
Brownlee expects to find in the dust brought by the spacecraft evidence of the formation of the solar system, and perhaps even of the birth of the universe itself. "We expect to understand how the comets were formed and what they are made of. We believe they are leftovers from the building materials of the outer planets." Brownlee believes that the comet's particles, made mostly of ice and dust, have been kept frozen since the birth of the solar system about 4.6 billion years ago. Such particles can usually only be found in the outer solar system, Brownlee believes, and they are destroyed when they approach the sun.
The Stardust spacecraft will be the first to bring dust from the tail of a comet to Earth. If it completes the mission, it will be the first time a spacecraft brings material that is not from the Moon to Earth. The comet orbits the sun in an outward orbit, at its farthest point, the orbit of Uranus and approaches the orbit of Neptune. At its closest point to the sun, it is near the Earth's orbit. The meeting with him will be held when he will be at a distance of about 180 million km from the sun.
On September 10, 1974, there was a change in the orbit of the comet. It approached the planet Jupiter and it deviated from its orbit. As a result, its orbit became shorter and it came closer to the Sun and the Earth's orbit (a distance of about 30 million km from the Earth's orbit). Its relative proximity to Earth makes it possible to send a spacecraft to it and also to return it at a relatively low cost, about 200 million dollars. Stardust was preceded by the European spacecraft Giotto, which the European Space Agency launched in '86 to chase another comet - Halley - but Giotto was launched for photography purposes only and was not returned to Earth.
Stardust is scheduled to rendezvous with Comet Wilde on January 2, 2,004. Then the spacecraft will pass at a distance of about 120 km from the comet's main body, and then it will also be able to capture small particles from the star's mantle - a region of dust and gas that surrounds its nucleus. The meeting will be broadcast on a special camera for Earth. Stardust will be powered by solar energy and will travel about 5 billion km.
It will stay in space for a long time - seven years - and make three loops around the sun. In the second and third rounds, the orbits of the spacecraft and the comet will approach. The spacecraft will send images from the encounter with Wilde, 2 a count of the amount of particles from the comet that hits the spacecraft and a preliminary analysis of the composition of the materials.
On its way, the spacecraft will also collect some interstellar dust, including dust from the recently discovered stream that moves from the solar region towards the Sagittarius system. The dust contains remnants of the material from which the solar system was formed. It may provide important information on the development of the sun and the planets, and perhaps even on the origin of life itself - simple organic substances, including amino acids, which scientists believe arrived on Earth in its early days as a result of collisions with comets.
The encounter between the spacecraft and the comet will last 12 hours, but according to Brownlee, its most complicated phase will last only a few minutes. At this stage, a special collection system will come out of the spacecraft that will capture particles that will move in its direction. At the base of the system is a board made of a material called aerogel. This material is supposed to absorb the tiny particles - smaller than a grain of dirt and nine times faster than the average speed of a rifle bullet - without causing them damage or changing their shape.
The airgel, known as "frozen smoke", resembles foam plastic, but is smooth as glass. 99.9% of it is air. A block of such material in the volume of a human body weighs less than half a kilogram, but it can carry the weight of a small car without collapsing. The scientists hope that it will be possible to extract the grains from the airgel tablet intact. In 2006, as the comet moves away, the collection system will return to the spacecraft compartment and descend into the Great Salt Desert in Utah. From there the particles will be transported to the Johnson Space Center in Houston.
"The Stardust spacecraft was launched yesterday to meet a comet. Yesterday at 23:04 the Stardust spacecraft was launched into space. The spacecraft is scheduled to arrive in 2004 near comet Wilde 2. In the next seven years it will travel five billion kilometers, and eventually return to Earth with a sample of dust from the comet's tail. In doing so, it may make history: the first spacecraft to meet a comet will return to Earth and bring with it material that is not from the moon. The spacecraft was supposed to be sent into space yesterday, but a momentary power drop disrupted the control room's radar device, and the engineers had to cancel the launch two minutes before the scheduled time.
