nPosted on September 21, 2017
n
Key Points
n
n
nToday’s historical anniversary is quite appropriate:
n
n
n
nOn this date in 2003, the spacecraft named Galileo ended its mission by entering Jupiter’s atmosphere – to be crushed and to burn up.
n
n
n
n
n
n
n
nWhy did I say it was appropriate? Because this year (2017), on September 15 (about a week ago), the spacecraft named Cassini ended ITS mission by entering Saturn’s atmosphere – to break apart and burn up.
n
n
n
n
n
n
n
n
n
nThese “death dives” were conceived to make sure that the planets’ moons, which might possibly be homes to some primitive lifeforms, will not be contaminated with Earth organisms (bacteria, etc.). There is no way for the gas giants themselves to have any sort of life-as-we-know-it, and the extreme heat as the spacecraft burn up in the atmospheres would ensure that the remaining materials would be sterilized.
n
n
n
nBut the death dives are more than just a handy way to avoid contamination. These dives give us a bit more data to go along with all the data the probes already provided during their lifetimes. Scientists are pretty sure they know many aspects of the atmospheres and other conditions on the gas giants, and so they are able to make predictions of the conditions the spacecraft will encounter on their suicidal dives. The spacecraft keep transmitting until they break up, or are crushed, so we are able to compare the predictions with the actual measurements taken and with the behavior of the spacecraft.
n
n
n
nHere are some comparison stats of the two spacecraft:
n
n
n
n
Launch dates:
Launch dates: n
nGalileo – October 18, 1989
n
nCassini – October 15, 1997
n
n
n
nPlanned mission lengths, including travel time:
n
n
Galileo – a bit more than 8 years
Galileo – a bit more than 8 yearsn
nCassini – about 10 years
n
n
n
n
Actual mission lengths, including travel time:
Actual mission lengths, including travel time:n
nGalileo – almost 14 years!
n
nCassini – almost 21 years!
n
n
n
nGalileo lasted six years longer than planned, and Cassini lasted more than a full decade longer than planned! Wow!
n
n
n
n
n
n
n
n
n
nHere are a few highlights of Galileo‘s findings:
n
n
n
nDiscovered the first asteroid moon
n
nFirst direct measurement of Jupiter’s atmosphere
n
nFirst asteroid flyby
n
nObserved Comet Shoemaker-Levy 9’s collision with Jupiter
n
nObserved volcanoes erupting on Io (a moon)
n
n
n
n
n
n
n
nObserved Io’s interaction with Jupiter’s atmosphere
n
nTheory of liquid ocean under moon’s ice supported (but not yet confirmed) – Europa
n
nProbable liquid saltwater layers under moons’ ice – Ganymede and Callisto
n
n
n
n
n
n
n
nMagnetosphere detected on Ganymede
n
nExosphere detected around three large moons
n
nFaint ring system detected around Jupiter
n
n
n
n
n
n
n
n
n
n(I covered some of Cassini’s findings here and here.)
n
n
n
n
n
n
n
n
n
nAlso on this date:
n
n
n
n
n
n
n
n
n
n
n
n
n
nIndependence Day in Malta
n
n
n
n
n
nIndependence Day in Armenia
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
nPeace One Day
n
n
n
n
n
n
n
n
n
n
n
nIndependence Day in Belize
n
n
n
n
n
n
n
n
n
n
n
nAnniversary of the approval of the first female Supreme Court Justice
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
nRosh Hashanah
n
n
n
n
n
n
n
n
n
n
n
n
n
n
nIslamic New Year (Al Hijra)
n
n
n
n
n
n
n
n
n
n
n
n
n
n
nPlan ahead:
n
n
n
n
Check out my Pinterest boards for:
Check out my Pinterest boards for:
n
- n
-
nSeptember holidays
n
-
nSeptember birthdays
n
-
nHistorical anniversaries in September
n
n
n
n
n
n
n
nAnd here are my Pinterest boards for:
n
- n
-
n
-
n
-
n
n
n
n
n
