We are so used to picturing
us humans on Earth's surface (and maybe soon Mars) that when we see a planet
like Jupiter, one of the first questions that comes to mind is "Can we
stand on it?" Let’s for a moment ignore
the extreme conditions (gravity, atmospheric pressure, high temperature, and
winds) that are found on the giant planet, and let’s just descend through the
atmosphere.
What we’d really see is a spectacle
like no other. Far beneath Jupiter's atmosphere is a gigantic ocean of liquid
metallic hydrogen, which would look and behave like mercury except that
hydrogen has 60 percent the density of water. So, you would have to sink for
tens of thousands of kilometers to reach a hot, molten, rocky core that's
possibly solid.
The interior of Jupiter is
not precisely mapped – that is one of the scientific goals of the Juno mission,
which has just reached Jupiter. The probe will use precise gravitational and
electromagnetic measurements to map what goes on underneath Jupiter’s clouds.
I know that the answer so
far is not really satisfying, so let’s drop the pretense of a magical observer
and let’s dive into Jupiter with current technologies.
Jupiter is really warm, with
the very top of its atmosphere at about 900 Kelvins (630°C or 1,160°F). As we fly
down through the atmosphere, the temperature quickly drops as the pressure and
wind speed increase.
Following what happened to the Galileo probe, which dived
into Jupiter in 1995, things start going badly for electronics 58 minutes into our
exploration and 156 kilometers (97 miles) into the atmosphere. For the Galileo
probe, this combination of pressure (23 atmospheres) and temperature (153°C or 307°F) proved deadly.
But it's been 20 years, so
let's assume we can continue down. At 500 kilometers (310 miles), the
visibility is almost completely gone and the thick ammonia clouds swirl all
around us, with wind speeds of around 100 meters (330 feet) per second.
Underneath the ammonia
clouds, there are more water clouds and more complex atmospheric effects that
Juno will hopefully clarify. Current technology will have been pulverized by
now, and our remains will now be traveling to a layer of supercritical fluid
hydrogen – something not quite a gas but not exactly a liquid either.
After about 2.5 hours of
exploration, we will have reached the liquid metallic hydrogen ocean. Heavy
elements might reach the center after many more hours of falling. So, you
couldn't exactly stand on this ocean. But below this, it's thought Jupiter may
indeed have a rocky core, perhaps somewhat similar to terrestrial planets. Juno
will help answer this question during its mission.
Jupiter has most of the
planetary mass of the Solar System, and could easily fit all the other planets
in its interior.
There's a reason why it is
the planetary king of the Solar System.