For this episode of Western Slope Skies, a look at the moons of Jupiter, and the two Galileos - the man and the machine.
In 1610, Galileo Galilei became the first person to observe another planet, Jupiter, and its 4 largest moons, Callisto, Europa, Ganymede, and Io. For the next 380 years, most scientists believed that those moons were similar to our Moon, that is, rocky spheres without activity or atmosphere.
As technology improved, theories emerged that perhaps the moons of other planets, especially Jupiter and Saturn, were much more interesting than our Moon.
In 1989, NASA launched the Galileo mission to Jupiter to evaluate these theories. Arriving in 1995, Galileo’s observations have changed how we view the moons of other planets.
Images show remarkably different surfaces on the four major moons with striking colors.
Interestingly, the visual camera on Galileo was one of the first astronomical applications of CCD technology. The sensor was 800 pixels by 800 pixels. Today’s smartphones far surpass this in resolution.
Other data captured by Galileo provide strong evidence that:
• Europa has a liquid ocean beneath its icy surface.
• Ganymede and Callisto also have saltwater regions beneath their surfaces.
• Io has VERY active volcanoes, which indicate a partially molten mantle.
• Ganymede has a strong magnetic field, the first for a moon.
• Europa, Ganymede, and Callisto have thin atmospheres.
There are 67 confirmed moons of Jupiter. Most of them ARE dead, inactive rocks.
To avoid possible contamination of the moons, in 2003, Galileo was deliberately navigated into Jupiter’s thick atmosphere at 108,000 mph where it vaporized.
In 1996, the US and Europe launched Cassini-Huygens. The mission: to study Saturn and the major moons of Saturn. Cassini’s discoveries have paralleled the Galileo mission in that the major moons of Saturn have proven to be intriguing beyond anyone’s imagination.