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Planetary Science

¨  Do you have information on the status of any non-Antarctic meteorite collection projects?
¨  Have spacecraft landed on all terrestrial worlds? If not, where have they landed?
¨  What would it be like adapting to life on Mars?  How would you grow food?
¨  What did the Mars rover get stuck in and how did it get out?
¨  What is the history and origin of planetary geology?
¨  Is it rumor or truth that Titan might contain liquid methane or other hydrocarbons?

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[Links provided here were valid at the time the question was answered.  If you find a broken link, please Contact Us so we can remove it.]

I am mentoring an advanced junior in high school on a science project involving the collection of iron micrometeorites.  She can find a wealth of published info on the Antarctic collections, but is having difficulty finding source material for terrestrial collections.  As she has begun her collections using several methods (particularly during the Leonid shower and post-shower rains), she wanted to know of current terrestrial-based projects.

ANSWER from Imagiverse on 20 December 2006:
Meteorite expert Chris Herd asked me to forward this message that he received from a colleague at Athabasca University:

I would say my hunt for micrometeorites was not very successful.  I happen to have come across other materials suggesting trying it and thought I would send on for your interest or opinion:


a site with a lot of emphasis on other things than micrometeorites is


and the fact that they don't much mention micrometeorites must be significant.

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Have spacecraft landed on all terrestrial worlds?  If not, where have they landed?

ANSWER from Stephanie Wong on 6 August 2006:
Nope!  There have been landing missions to Venus, Mars, Earth's moon and Saturn's moon Titan.  There has even been a spacecraft that had a "controlled crash" landing on the asteroid Eros.  As for non-terrestrial worlds, probes have been sent (intentionally and as a mission-completing last hurrah) down into the atmosphere of Jupiter.

You might find this website informative:

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What would it be like adapting to life on Mars?  How would you grow food?

ANSWER from Stephanie Wong on 24 February 2006:
There are many difficulties to adapting to life on Mars.  For long-term stays, you must be able to provide self-contained living quarters because the Martian environment is deadly to the unprotected human.  There is not enough oxygen in the atmosphere (almost none), the atmosphere is thin, you'd probably choke on the fine and corrosive Martian dust, the temperatures are frighteningly cold, etc.  So, provided you have a sealed habitat, one thing that you will notice is that you only feel 1/3 as heavy as you would on Earth.  That might be an adjustment for you, although I am not too sure about any health effects on the lower gravity (whether you need to exercise more to prevent bone loss).  Your habitat needs to be shielded from the harmful cosmic/solar radiation coming down at you since there is no ozone or global magnetic field to shield you.  There are just a few things that you need to "adapt" to.

Food must be grown in a self-contained greenhouse.  The abundant carbon dioxide in the atmosphere will provide the CO2 needed for photosynthesis.  However, you must have a generator of some sort to somehow convert the CO2 into water, or be able to tap into the icecap or possible subsurface ice in order to get water.  You would probably have a hydroponics system since Martian soil is likely not fit for terrestrial plants.

I hope I made a good start for you to read further.  Please check out this website: http://science.nasa.gov/headlines/y2004/25feb_greenhouses.htm

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I visited JPL this summer when one of the robots got stuck in a patch of 'something'.  By simulating the texture in the Mars simulation room, scientists were able to devise a scheme to rock the robot out of the 'something'.  I was told that scientists and engineers were now debating whether the robot should go back and 'see' what the something was or get the heck out of there.  Can you tell me what the outcome was?

ANSWER from Stephanie Wong on 21 February 2006:
The Mars Exploration Rover Opportunity got stuck in a sand dune (nicknamed Purgatory Dune) in the spring of 2005.  It isn't really a special "something", just a run-of-the-mill sand dune which is found everywhere on Mars.  I'm not sure what the mission team would be looking for.  Perhaps they were talking about snapping some pictures of the rut that Opportunity's wheels made.  Since the rover's wheels started slipping when it started to get stuck in the dune, it would have created a miniature "ditch".  In the process of backing out of the dune, a careful process that took weeks of planning and execution to do, I suspect the ditch would have become even larger.  Had the ditch been deep enough to get past all that uninteresting dune material and into the real ground layer, then the scientists would have been interested in investigating the hole.  Of course, that decision would have had to be balanced by the fact that because the rover got stuck in that area once, it would have been wise to get out of there as soon as possible, lest it get stuck again.  I suspect the reason for analyzing the region around Purgatory Dune was to see the terrain and devise plans on how to detect similar terrains to prevent themselves from getting stuck in in again.  Close inspection of the sand grains would also tell them about the physical properties of the dune which could be used to devise "rescue" scenarios.  It appears that the rover backed out of the dune a number of feet before taking some shots of the "trap".  You can get further details by reading some of the press releases (with pictures):

Opportunity has traveled far after crawling out of that dune. I find these traverse maps cool:

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What is the history and origin of planetary geology?

ANSWER from Roger Herzler on 26 January 2006:
Please refer to the interviews of scientists on our Interview pages which includes planetary geologists Phil Christensen, John Grant and Vicky Hamilton.

There may not be a specific answer to the question of the true 'origins' of "planetary geology".  It is much like asking "who discovered Mars?"  What makes up the geology of other planets has undoubtedly been a topic of study for centuries.  However, we can discuss astrogeology as it has existed in recent times.

The study of geology and forces that affect the geology of other planets, also known as 'astrogeology', likely got it's start as a part of other official fields of study such as "astronomy" in the 19th century.  However, that is suposition on my part - I have no cite for that information.  I also believe it makes sense that it got its start in earnest when telescopes began to show enough surface detail of other planets (and our Moon) to allow for study and speculation.  Today, it has progressed into the 21st century with the landings and visitations of various probes on planets like Mars, Jupiter and Venus.  Without a doubt, technologies such as radar, infrared and spectral analysis devices have also improved the field.

The actual answer for "when" the field got started may not be answerable (I couldn't find it), but it probably is closely aligned with the ability of scientists here on Earth had in making observations of other worlds.  The better that ability got, the more intense the study of other planets' geology.

Wikipedia (http://en.wikipedia.org/wiki/Astrogeology) cites credit given to Eugene Shoemaker for creating the field within the US Geological Survey, but from my perspective I believe the study of other planets pre-dated his participation in the field under an 'official' name like "planetary geology".

Related external links:

USGS Astrogeology Page

Arizona State University Planetary Geology Group

NASA Planetary Geology Educator Guide

NASA Planetary Geodynamics Lab

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Scientists have long speculated that Titan might contain liquid methane or other hydrocarbons is it a rumor or truth?

ANSWER from Stephanie Wong on 1 October 2005:
It is absolutely true!  Titan, which is much farther away from the sun than the Earth, cannot have liquid water.  Water is solid as rock at those temperatures.  However, these are temperature where hydrocarbons, like methane, are cold enough to condense into liquids.  Evidence of these liquid hydrocarbons on Titan is extensive.  Recently, the Cassini spacecraft and its probe Huygens found evidence of channels that to utmost certainty, were carved out by liquid hydrocarbons.  In fact, one could say that Titan has a "hydrocarbon cycle", rather than Earth's hydrologic cycle.

You can read more about Cassini's latest discoveries at:

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2 July 2007

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