30 May 2011
Forty years ago Monday a tiny spacecraft was launched from Cape Canaveral in Florida. It was unmanned, weighing in at about a ton, and had a half-year journey to reach its destination - Mars. The orbiter was Mariner 9.
The Mariner program was set up in the 1960's by NASA to explore our neighbors Mercury, Venus, and Mars. Several early Mariners were sent to Mars but only as "fly-by" missions, literally flying by the planet, snapping off pictures as they passed.
Mariner 8 and Mariner 9 were sisters and were to be the first planetary "orbiters," spacecraft which are fired off towards a planet, slowed down as they approach it, allowed to establish an orbit, and then take images at their leisure.
Accomplishing a fly-by is complicated enough; trying to shoot a tiny car-sized object from a huge, spinning planet to another moving planet tens of millions of miles away. Now imagine trying to manipulate it so that it can slow down at the just the right time, at the just the right rate to be able to skim just close enough to the surface so it can now be a satellite of the planet circling at just the right distance. Those kinds of calculations require the brains of a rocket scientist, actually many of them.
Mariner 8 was launched first, on May 9, 1971, but malfunctioned on liftoff and ended up in the Atlantic Ocean, over 77 million miles off-course.
It was up to its sister, Mariner 9, to keep hopes of a Mars orbiter alive - and this craft did not disappoint.
Launched just weeks after, on May 30, Mariner 9 made a flawless journey to the Red Planet arriving there in mid-November only days before a competing Soviet craft. After orbiting for a couple months - until horrendous global dust storms would calm down - she started sending back the most detailed views of the fourth rock from the sun anyone had ever seen.
What did these images reveal? That Mars had a huge volcano, Olympus Mons, the largest in our solar system. That there was a valley on Mars so long that it makes our Grand Canyon look like a bug bite. Named Valles Marineris after the spacecraft, the gigantic gorge is as long as the United States.
Mariner 9 also sent back detailed images of the polar ice caps, and the moons, Phobos and Deimos.
Where is it now? Still in orbit. The spacecraft was "turned off" long ago but will continue to circle Mars for another decade until it sinks low enough in orbit that it will crash into the red rocks of Mars.
All the lessons learned in the Mariner program blazed the trail for the next generations of spacecraft which have given us volumes of information about this perfectly designed solar system we call home.
16 May 2011
After teaching about it for years in science classes, I only recently got to personally experience what getting an MRI (Magnetic Resonance Imaging) is all about.
It was kind of a letdown. Knowing I was to be inserted into a gigantic magnet that could help other instruments see what was inside of me, I was hoping to feel something - anything. Alas, although it was loud, it was non-eventful.
I was in a machine that has literally tens of thousands of times the magnetic force of our entire planet... and I almost dozed off.
If a person is not even aware of an intense magnetic field while being immersed in one, can such a weak field as Earth's have any effect on life? You betcha.
Below our feet, down around the core of the Earth, are slowly churning columns of molten iron and nickel. This swirling generates an all-encompassing magnetic field around our planet. Anyone who has owned a compass can see the field's effect as the needle lines up in the direction of Earth's magnetic field lines.
One of the unsung characteristics of our subtle magnetic field is that it is absolutely necessary. It protects us; it is like a shield about us. Shielding us from what?
Mainly from the solar winds - very fast moving charged particles emanating from the sun. When a racing charged particle encounters a magnetic field it is deflected. Thus the solar wind is pushed aside by our field and is unable to crash into Earth head-on.
This has profound benefits for life which does not exactly need speedy, charged particles crashing into them, causing mutations and damaging tissue. And since the solar winds are part of a mechanism that tears water from a planet, our atmosphere and water cycle are also safe.
Neither of our rocky neighbors, Venus and Mars, have magnetic fields. Nor do they have the water they once had. Nor do they have life.
The magnetic field around our planet is not very strong compared to what we can produce in a laboratory, but it is just enough for us to enjoy life on this beautiful planet, and it all works quietly in the background.
Next time you play with a magnet, or watch a compass needle fix position - or are subject to an MRI - be reminded that we are all surrounded by an invisible, quiet force that keeps us safe.
Until next time, clear skies!
02 May 2011
We haven't looked at the naked eye sky in a while here. Let's take a look!
These are the last days to see mighty Orion, the king of the winter skies, as he glides off into the sunset in the west. No worries; we'll see the big guy and his other hibernal neighbors again later in the year.
So let's switch our attention to some easily spotted sky markers to get a feel for what's coming up this summer.
Starting in the north find the Big Dipper, that big slab of star property in the constellation Ursa Major, higher in the sky now than many people are used to. It is completely turned "upside down" in the early evening at this time of the year. Its two stars farthest to the west, Dubhe and Merak, are the end of the pot side of the Dipper and point directly down to Polaris the North Star.
Go to the "handle end" stars of the Dipper. Let's use those as pointer stars to do a quick walk across the sky. See how they point away from the "bowl" towards a very bright star, almost due East, called Arcturus. Located in the constellation Boötes, Arcturus is about 30 times bigger than our sun and pours out nearly 300 times the energy. It is at a magnitude -0.7, which translates in layman terms to "really, really bright." Arcturus will play a starring role in the skies throughout the summer.
Continue to "arc" a curve through Arcturus over to next bright star, Spica, in the southeast. Now reappearing in our skies after leaving us last year, Spica is in the constellation Virgo and is over 250 light years away - thankfully. It is an intense star as far as energy output goes. Spica is only 10 times bigger than our sun, but because of the physics of that type of star, that's enough to produce nearly 15,000 times the energy. It would be a death star if it were rooming with the sun.
It is in that same part of the sky we will see another heavenly body not light years, but mere light minutes away. Saturn, our ringed friend, is just a few degrees above Spica. The tiny golden orb will be there, stuck near Spica, for the rest of the summer. Please get hold of a telescope this summer and take a look. A look at Saturn through a scope is on the bucket list for any true sky lover.
Through the next months we will occasionally look more deeply at some of the other summer stars and constellations in an attempt to get to know our skies better.
Until next time, clear skies!