After nearly four years of glorious service to science, the European Space Agency’s Herschel Space Observatory mission has come to the end this week. Running out of helium coolant needed to chill its instruments down to near absolute zero means that it has closed its far-infrared eyes to the Universe for good. After a few final tests, controllers will park the retired probe in a permanent solar orbit.
Its mission was a far-reaching one – to study for the first time some of the coldest regions of space and examine the molecular chemistry of objects across the Universe- from distant galaxies and newborn stars to the atmosphere’s of gas giant planets and comets. (Related: Starburst Galaxy could Illuminate Early Universe)
But one of the stand-out legacies of Herschel, according to Michel Fich, one of the of mission scientists, will be how the space telescope has provided a much greater understanding of the abundance of water outside of Earth and the solar system.
Herschel has helped provide answers in regards to how water may actually get onto planets, even habitable ones, like our own, says Fich.
“We believe that life requires water and all life as we know it is closely tied to its presence,” said Fich, astronomer at University of Waterloo, Ontario, Canada.
“So a question about life in the rest of the Universe has to start with questions like: Is there lots of water in the rest of the Universe? Is water found in high abundance in other solar systems?”
Here are Fich’s four picks for Herschel’s big watery discoveries.
1. Cosmic reservoirs of water that pepper star birth regions
Peering at a cosmic cloud of gas and dust that is on the verge of collapsing and forming sun-like star and planets around it, Herschel discovered enough water vapor inside this nebula to fill Earth’s oceans more than 2000 times over.
This observation in the constellation Taurus is the first detection of water vapor in a cold molecular cloud, and shows that there is a lot of water in the original clouds that will eventually form a star, and a solar system around it.
2. Creating a solar system with a huge amount of water
This artist’s impression illustrates an icy protoplanetary disk around the young star TW Hydrae, located about 175 light-years away, where Herschel found a disk around the newborn star that is saturated with water.
This find for the first time shows that water can migrate from the original stellar cloud to the surrounding disk that may one day fragment into planets.
3. Evolution of a comet system around a very young solar system
Herschel has studied the dusty belt around 25 light year distant star Fomalhaut and determined that it formed from the ongoing collision of thousands of icy comets..
The big questions facing astronomers now is if this cometary debris will go into making planets, is expelled from the solar system, or form comet belts?
4. Supporting evidence for theory that the Earth’s oceans come from comets
Herschel studied comet Hartley 2 using the most sensitive instrument to date for detecting water in space, and has shown that this cosmic iceberg is packed with water that has the identical molecular fingerprint as those found in Earth’s oceans.
The discovery revives the idea that our planet’s seas may have come from comets – presumably falling onto the Earth’s surface after the planet had already formed. (See: What Created Earth’s Oceans: Comet Offers New Clue)