Spacecraft may still yield data
The inner solar system is a realm of rock and metal: Mercury, Venus, Earth and Mars have surfaces on which you can stand.
The outer solar system is a realm of gas and ice: Jupiter Saturn, Uranus and Neptune are huge, but their “surfaces” are made of clouds.
The solar system was born four-and-a-half billion years ago, as a spinning cloud of gas and dust – the solar nebula – collapsed inward. In the hot, high-pressure center of the nebula was born the sun.
Close to the sun, the inner planets formed out of materials – rock and metal – that could take the heat.
Volatile materials – those easily turned from liquid to gas – were vaporized and blown outward.
So how did oxygen, which (on Earth) turns to gas at any temperature above 300 degrees below zero Fahrenheit, survive the heat?
You’ve got to heat a ruby to over 5,000 degrees Fahrenheit before it will melt. Even more to get it to boil.
Aluminum oxide – made of aluminum and oxygen atoms, and which, in its red gem form, is ruby – is one of the least volatile substances known. Many types of atoms survived conditions in the inner solar system by combining to make such refractory – non-volatile – minerals.
Temperature and volatility explain why we find some atoms here, other atoms there. But looking more closely, these factors alone don’t explain all the patterns. The early solar system must have gone through a number of different distillations.
To understand how the planets formed we must discover the composition of the solar nebula, four-and-a-half billion years ago.
The solar nebula no longer exists. But the surface of the sun should retain nearly the same composition as that ancient cloud of gas and dust.
The sun is way too hot to grab a sample – a spacecraft would vaporize.
The eerie blue “ion tail” of a comet and the northern lights bear witness to a stream of particles blown out from the sun at half-a-million miles an hour or more: the solar wind.
For two-plus years, the Genesis spacecraft hovered at a balance point – a “Lagrangian point” – between Earth and sun, collecting atoms of the solar wind as they embedded themselves in fragile collector plates and foils of silicon and sapphire, diamond and gold. Then the spacecraft fired its jets and put itself on course to return to Earth.
Roger Wiens (“weens”) is project leader for one of the Genesis experiments. He told me how design engineer Steve Storms had, in his opinion, “over-engineered” the instrument, putting in, for instance, shock-absorbing springs. The returning spacecraft, after all, would be slowed, first by air resistance; then by a parafoil (a parachute/wing); finally by a helicopter, which would catch the spacecraft by snagging the parafoil in mid-air.
Watching the spacecraft’s descent on NASA TV just over two weeks ago, friends and I watched the spacecraft screaming in through the atmosphere, a white-hot meteor … it grew larger … we could see its saucer shape … we could see it tumbling … we began to wonder, “Where is the parachute?!?”
The parafoil never deployed. The spacecraft struck the Utah desert at close to 200 miles an hour. The collector plates shattered, instantly exposed to air and moisture.
And yet, impacting at half-a-million-miles an hour, many of the sample atoms lodged themselves beneath the surface of the collector plates – and may be retrievable. Thanks to the “over-engineering” of his experiment, Wiens is optimistic he’ll get some good data. His first reaction when he saw his design engineer: “I hugged him!”
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