[Az-Geocaching] Mars Approaching (Warning: Off-Topic)
Jim Scotti
listserv@azgeocaching.com
Thu, 31 Jul 2003 16:43:04 -0700 (MST)
Hey Trisha,
Mars is putting on a great show these nights - bright and red. I saw it
peeking through the monsoon cloudy skies last night for the first time in a
week or so! I'd recommend for all those interested to visit your local
planetarium/telescope and get a good look. Also, keep an eye out for a Mars
Star Party that I'm sure the local amateur astronomy clubs will be putting
on. They have much better equipment than most people and are usually more
than happy to show off things in the night sky.
The best time to view Mars is when it is at its closest which happens when
the Earth and Mars line up on the same side of the sun. When this happens,
it is called opposition. The orbits of both Earth and Mars are not perfect
circles, so the distance to Mars during oppositions varies considerably.
When Mars is near its "perihelion", at its closest approach to the sun each
Martian year to the sun (which is 687 Earth days long) it is only 207 million
kilometers from the sun but when at its aphelion, at its farthest from the
sun, it is about 250 million kilometers from the sun (compared to Earths
average distance from the sun of about 150 million kilometers). By
comparison, Earth's orbit is much more circular ranging from 147.5 to 152.5
million kilometers from the Sun. So, whenever the Earth and Mars line up,
which happens about every 780 days, the distance between them can vary
between 100 million kilometers if Mars it near its aphelion and about 57
million kilometers when Mars is near its perihelion when aligned with Earth.
It just so happens that this next month, Mars will be near its perihelion
when it passes through opposition so it will be near its closest possible
approach to Earth and therefore bigger and brighter than during most other
Martian oppositions, so enjoy the show! Also, Earth is close to its aphelion
(which happens in July), so that makes a difference of a couple million
kilometers (small change compared to the affects of Mars eccentric orbit on
the story, but significant enough).
If you really want to see Mars up close, check out the Mars Global
Surveyor webpage - there are lots of wonderful places that I'd like to hide
geocaches on Mars - imagine a hike to the bottom of Valis Marinaris, a canyon
larger than our Grand Canyon or to the top of Olympus Mons, the largest
mountain in the Solar System. Here's a URL that will allow you to browse
through some of those wonderful pictures: http://mars.jpl.nasa.gov/mgs/ - if
you click the top link labeled "MOC Images with Captions..." to see some of
the best examples which are released as "pictures of the day". These
pictures have really changed my view of Mars from one of a distant planet
with images from earlier spacecraft that made it look a lot like our own moon
looks through a telescope to an actual place that you could put hiking boots
on and go out and explore. Here's a few interesting images in particular:
http://www.msss.com/mars_images/moc/2003/07/25/index.html - These are a bunch
of sand dunes that look like fortune cookies and are all very similar in
appearance.
http://www.msss.com/mars_images/moc/2003/06/05/index.html - Mars has dust
devils, just like we see here in Arizona. Here is a picture of the tracks of
some dust devils across the Martian surface.
http://www.msss.com/mars_images/moc/2003/06/11/index.html - Here are some
gullies on the side of a crater wall.
http://www.msss.com/mars_images/moc/2003/06/10/index.html - There's also
frost on Mars, in this case, carbon dioxide frost near the Martian poles.
And this is a real color image too!
http://www.msss.com/mars_images/moc/2003/07/11/index.html - This is a view of
a small canyon feature - is it a crack or water erosion?
You can also find pix of Mars moon Phobos and a picture of the Earth and Moon
as viewed from Mars if you look around a little bit on these webpages. Some
of the images are a bit big, but IMO, they are worth the wait for downloading
and in any case, there are some thumbnails that you can see before starting
the bigger downloads....
Any of you geocachers have telescopes? It might make for a great event
cache one of these nights if so. I don't have anything bigger than a
spotting telescope these days - I guess I'm too spoiled using the bigger
telescopes I use every month up on Kitt Peak.
Jim.
On Thu, 31 Jul 2003 trisha@brasher.com wrote:
> Hey there Jim Scotti!
>
> Any info you can give us about this up coming astronomical event? It
> sounds pretty cool!! (With our luck, we will end the 5-year drought
> with a huge monsoon season and have cloud cover for the next two
> months!!)
>
> (SPOILER: for those of you who are preterbed by off-topic posts, I
> posted this to the list on purpose because I... 1) wanted to ask Jim
> and 2) thought there might be a number of others on this list who
> would be interested in astronomy. So, if you are not interested, just
> delete this and any other upcoming posts with "Mars" in the title.
> Simple. Thanks)
>
> Trisha "Lightning"
> Prescott
>
> INFO:
>
> Never again in our lifetime will the Red Planet look so
> spectacular!
>
> This month and next Earth is catching up with Mars, an
> encounter that will culminate in the closest approach between the two
> planets in recorded history. The next time Mars may come this close is
> in 2287.
>
> Due to the way Jupiter's gravity tugs on Mars and perturbs
> its orbit, astronomers can only be certain that Mars has not come this
> close to Earth in the last 5,000 years but it may be as long as
> 60,000 years. The encounter will culminate on August 27th when Mars
> comes to within 34,649,589 miles and will be (next to the moon) the
> brightest object in the night sky. It will attain a magnitude of -2.9
> and will appear 25.11 arc seconds wide. At a modest 75-power
> magnification Mars will look as large as the full moon to the naked
> eye.
>
> Mars will be easy to spot. At the beginning of August, Mars will rise
> in the east at 10 p.m. and reach its azimuth at about 3 a.m. But by
> the end of August when the two planets are closest, Mars will rise
> at nightfall and reach its highest point in the sky at 12:30 a.m.
> That's pretty convenient when it comes to seeing something that no
> human has seen in recorded history.
>
> So, mark your calendar at the beginning of August to see Mars grow
> progressively brighter and brighter throughout the month.
> Share this!
>
> No one alive today will ever see this again.
>
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> "Although no one can go back and
> make a brand new start,
> Anyone can start from now and
> make a brand new ending."
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Jim Scotti
Lunar & Planetary Laboratory
University of Arizona
Tucson, AZ 85721 USA http://www.lpl.arizona.edu/~jscotti/