Collecting Interplanetary Dust Particles.
THE SMALLEST YET BIG ENOUGH TO STAY AROUND
In the introductory blog to interplanetary dust particles, we have learned that our Solar System requires a certain minimal size for the particles (1 μm) to be able to stay in our near surroundings. If the radiational force is stronger than the gravitational force of the Sun attracting the particles, the particles are thrown out of the Solar System.
TEN TIMES SMALLER THAN HUMAN HAIR
The majority of interplanetary dust particles floating between planets in outer space is between 1 μm and 50 μm in diameter, which is about a tenth the width of a typical human hair. Being so small, we need an electron microscope to study them. Now imagine the challenge to collect them.
COLLECTING AND ANALYSING IDPS
In 1950 scientists got an idea to start with collecting the dust particles that have already made it to the Earth's surface. Soon it was concluded, that it is almost impossible to separate extraterrestrial dust from terrestrial components. The next attempt was ten years later in the stratosphere. The stratosphere is the second layer of the atmosphere as you go upward, at the attitude of 20 - 37 km. Balloons with dust collectors were sent to the stratosphere in a rather unsuccessful mission. Balloons had to be replaced by high flying aircraft. At the time, the famous U2 spy plane was the first to come to mind. The plane was equipped with efficient dust collectors under the wings. It proved successful. U2 spy plane was later substituted with the aircraft ER-2 (on the image below), which has successfully collected hundreds of IDPs in further missions. Now we know, that the best place to collect the smallest particles in outer space is the lower stratosphere, where the particles are already slowed down yet still separated from the terrestrial material.
THE STARDUST MISSION
The space environment is surely the best place to collect extraterrestrial particles. But why stay in the Earth`s atmosphere and not go further in outer space. The idea to fly a spacecraft to land on a comet is present since the 80s, yet it was first in the year 1999 when Nasa launched a robot under the Project Stardust to fly by a comet Wild 2. After a seven-year-long journey, the capsule with a dust sample returned to Earth in 2006 with plenty of IDPs. In 2014 scientists announced, that next to interplanetary dust particles also possible interstellar dust particles were found in the capsule.