Archive for the ‘MGS’ category

AGU 2009 – Day 2

December 17, 2009

I started off day 2 of AGU at a couple of lunar talks showing off data from the Lunar Reconnaissance Orbiter. Unfortunately, I missed the early sessions about the high-res cameras, but the bright side was that I learned abount some instruments I was less familiar with. First was the Lunar Orbital Laser Altimeter – LOLA. A similar instrument on Mars Global Surveyor, MOLA, revolutionized our view of Mars. The MOLA map has become the standard to which all other mars maps are registered, and LOLA is going to do even better for the moon. LOLA works by sending five laser pulses in a pattern similar to the spots on the “five” side of a die. The spacecraft then recieves the reflected laser light and determines the distance to the surface, and therefore the topography. The advantage of having five spots is that it also gives astoundingly good measurements of the slopes.

Credit: NASA/LOLA team

After the LOLA talks, I heard about the results from the cosmic ray detector, CRaTER, on LRO. Apparently right now is a good time to observe cosmic rays because the sun is not very active. The current weak solar wind pressure allows more cosmic rays into the inner solar system! Understanding the radiation environment is important for sending hardware and people to the moon. One significant result that the CRaTER team reported was that even though the moon blocks cosmic rays as you get close to it, the total radiation increases because rays that hit the surface send up showers of secondary radiation. There is also no evidence that the amount of radiation on the moon decreases when Earth’s magnetosphere tail points toward the moon, as some people had suggested.

An animation of a cosmic ray hitting Earth's upper atmosphere. A similar shower of secondary particles is produced when cosmic rays hit the moon. Image creadit: U. Chicago

After that, I headed over to listen to Mars talks. Serina Diniega gave a nice presentation about her discovery of active gullies forming on dunes in the southern hemisphere. She showed evidence of several dune gullies for which there are “before and after” images showing noticeable changes. Serina suggested that frost accumulating in the upper alcoves of the gullies could trigger the changes, which would be consistent with the observation that most changes happened in southern winter. A related talk by Colin Dundas showed similar results, with HiRISE observations revealing fresh gullies on pole-facing slopes in the southern hemisphere.

An example of a fresh gully deposit in HiRISE image PSP_002200_1380.

After a few more Mars talks, I headed back to the moon to hear about LCROSS. I caught the tail end of a talk about the Lyman-alpha Mapping Project (LAMP) on LRO. This instrument uses the light emitted by hydrogen in stars to illuminate the dark craters on the moon, which is a really cool idea. Interestingly, the permanently shadowed craters look “dark”, implying that they contain something (ice) that absorbs UV light. LAMP also saw the plume kicked up by the LCROSS impact, and detected hydrogen emission, as well as, oddly enough, mercury (Hg) emission. Apparently, Mercury is volatile enough that over geologic time it also gets concentrated in shadowed craters. Future astronauts drinking the moon’s water will have to watch out for mercury poisoning!

Tony Calprete gave a nice overview of the LCROSS mission. He explained that the reason the plume wasn’t visible from earth was because they ended up selecting a crater that was known to have hydrogen, since LRO was going to be positioned to get good observations from orbit. He showed some of the spectra recorded by various instruments, which had evidence for all sorts of good stuff, including H2O, CO2, methane (CH4), SO2, ammonia (NH3), H2S, and even a couple of mystery lines that some people on the team think might be gold! (There’s gold in them thar hills?)

A second LCROSS talk by Peter Schulz focused on the cratering process. The most interesting aspect was the effect of a hollow projectile (such as the big empty centaur rocket used as the LCROSS impactor) on the plume behavior. It turns out a hollow projectile causes the crater ejecta to form a higher plume that spreads out less. He also pointed out that the reason the LCROSS impact did not look like the Deep Impact plume was because deep impact was a very high speed impact into a low-gravity object with a solid projectile, while LCROSS was a slow hollow impactor hitting a body with significant gravity.

Stay tuned for the Day 3 post, which will include some particularly interesting sessions about Venus and astrobiology and society!

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Be a Martian!

November 17, 2009

Fact #1: As a Mars scientist, I am incredibly spoiled. There are so many missions to Mars right now sending back so much data, that even if they all went silent tomorrow, it would be decades before we managed to look at all the data and figure out what it’s telling us.

Fact #2: There are lots of people out there (I’m looking at you, loyal readers!) who would love to be able to actively participate in exploring Mars. I mean, have you seen the stuff that the folks at UnmannedSpaceflight have managed to put together? They do more with the data from Mars than a lot of scientists!

So, given those two facts, you can see why I think the new “Be a Martian” collaboration between NASA and Microsoft is a great idea. Check out this excerpt from the press release:

Drawing on observations from NASA’s Mars missions, the “Be a Martian” Web site will enable the public to participate as citizen scientists to improve Martian maps, take part in research tasks, and assist Mars science teams studying data about the Red Planet.

“We’re at a point in history where everyone can be an explorer,” said Doug McCuistion, director of the Mars Exploration Program at NASA Headquarters in Washington. “With so much data coming back from Mars missions that are accessible by all, exploring Mars has become a shared human endeavor. People worldwide can expand the specialized efforts of a few hundred Mars mission team members and make authentic contributions of their own.”

How cool is that? It’s a really brilliant idea, and I hope it goes well. A similar project was pioneered by galactic astronomers who had way too many pictures of galaxies to deal with, so they opened up the database to the public in the form of GalaxyZoo. It was a tremendous success, with thousands of people helping to classify millions of galaxies.

I just created my account and played around a bit, and it looks like a very user-friendly introduction to Mars science. You can contribute in two main ways: aligning images to contribute to a global map, and also counting craters. Both of these tasks can sort of be done by computers, but humans will always be better.

There’s more to the Be a Martian site than just work though, there are also lots of goodies like videos and Mars wallpapers, and great information about Mars. There is even a “movie theater” where you can watch the first few episodes of a series of videos called “The Martians”, that focus on people from all over the country who are involved with Mars, ranging from members of the rover teams to enthusiastic amateurs to actors putting on a play about Mars! There are more episodes on the way, and I encourage you to keep watching… you might see someone you recognize. ;)

Bottom line, it looks like a great site, and a great way to get involved in Mars exploration and learn about everyone’s favorite Red Planet and the people who are fascinated by it. What are you waiting for? Head on over and sign up! I’ll see you on Mars!

 

The MOC “book”: Dunes, Ripples and Streaks

February 16, 2009

This is the fourth in a series of posts about the huge paper by Malin and Edgett summarizing the results from the Mars Orbital Camera’s (MOC’s) primary mission. If you’re just tuning in, get caught up by reading the first three posts, and if you want to read along, download a pdf of the paper here.

This week we’re looking at two sections: “Aeolian Processes and Landforms” and “Polar Processes and Landforms”. Also known as wind and ice features. These represent the most active features on the martian surface and they are also some of the weirdest looking! I’ll post about the aeolian features today and polar processes tomorrow since both have tons of images to go with them.

The authors make a distinction between dunes, which are always dark-toned and are likely made of sand-sized volcanic minerals, and ripples which are smaller, and are often light toned. This picture shows exactly what each term refers to:

Examples of dark-toned dunes overriding light-toned ripples.

Examples of dark-toned dunes overriding light-toned ripples. The arrows point to the most obvious places where the dunes are on top of the ripples.

The dark-toned dunes come in a variety of shapes, depending upon the amount of sand available and the wind direction. Figure 39 of the paper shows several of the types of dunes:

a) Thick sand sheet; b) These dunes are likely inactive - they have been eroded into more rounded shapes than you would expect to see on an active dune.; c) Barchan dunes near the north pole. d) Stubby barchan dunes. The wind is blowing from bottom to top in this figure ;e) Barchan dunes that extend far downwind (toward bottom right) become linear "seif" dunes ; f) Dunes near the north pole showing a "rectilinear" pattern.

a) Thick sand sheet; b) These dunes are likely inactive - they have been eroded into more rounded shapes than you would expect to see on an active dune.; c) Barchan dunes near the north pole. d) Stubby barchan dunes. The wind is blowing from bottom to top in this figure ;e) Barchan dunes that extend far downwind (toward bottom right) become linear "seif" dunes ; f) Dunes near the north pole showing a "rectilinear" pattern.

By comparing MOC observations with older Viking images, Malin and Edgett tried to detect evidence for dune movement. But even over 10-14 martian years, no dunes were seen to move. Not all dunes on Mars are inactive though: MOC did see streaks appear on the downwind sides of some dunes indicating that sand was moving.

An example of dunes with avalance streaks on their slip faces.

An example of dunes with avalance streaks on their slip faces.

As for ripples, they are almost everywhere on Mars. Interestingly, they are often much larger than ripples seen on earth, and they are always perpendicular to the wind direction.  When they are in troughs, they are always perpendicular to the trough trend, and they even “refract” around obstacles, following the surface winds.

The ripples are very similar in size to some of the ridged units mentioned earlier in the paper, but whether they are actually related is not clear.

Giant granule ripples. Notice that the ripples are oriented perpendicular to the trought that they are in, indicating that the wind that formed the ripples was blowing along the trough.

Giant granule ripples. Notice that the ripples are oriented perpendicular to the trough that they are in, indicating that the wind that formed the ripples was blowing along the trough.

Some of the most dramatic changes on the martian surface occur when dust is lifted or deposited, leaving either a dark or light wind streak. Wind streaks typically form behind some sort of topographic obstacle that disrupts the wind and causes turbulence which lifts dust, or alternately causes a space with less wind, causing dust to collect there.Some wind streaks are also composed of frost.

Large wind streaks composed of frost.

Large wind streaks composed of frost.

Hundreds of small wind streaks tracing the wind flow over topography. The surface is covered in frost and the narrow end of the streaks point downwind.

Hundreds of small wind streaks tracing the wind flow over topography. The surface is covered in frost and the narrow end of the streaks point downwind.

Dust devils are also very common on Mars, and they leave intricate patterns in their wakes as they vacuum dust from the martian surface. This figure shows a bunch of examples, including some dust devils caught in motion:

A collection of photos of dust devil streaks. c is a rare example of light-tones streaks, and h&i are examples of dust devils caught in action.

A collection of photos of dust devil streaks. c is a rare example of light-tones streaks, and h&i are examples of dust devils caught in action.

Of course, with the wind blowing sand and dust around on the surface, it makes sense that wind erosion is the most active erosional process on Mars today (unless you count the sublimation of the polar caps). Here is an example of terrain that has been eroded by the wind into a ridged and grooved pattern (also known as “yardangs”).

Most of the visible surface here is eroded by the wind into yardangs.

Most of the visible surface here is eroded by the wind into yardangs.

That concludes the aeolian section of the paper. Tomorrow I’ll be posting about polar processes, with lots more cool pictures!

ResearchBlogging.orgMichael C. Malin, Kenneth S. Edgett (2001). Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruise through primary mission Journal of Geophysical Research, 106 (E10), 23429-23570 DOI: 10.1029/2000JE001455

The MOC “Book”: Subsurface Patterns and Properties

February 15, 2009

The MOC paper saga continues. If you’re just tuning in, I’ve been writing a series of posts detailing a slow and detailed reading of the classic 2001 paper summarizing the results from the Mars Orbital Camera (MOC), the first high-resolution camera in orbit around Mars. Check out the previous posts here and here. Also, a reader pointed out to me that the full PDF of the paper is freely available at the author’s website! So if you’re interested, I encourage you to download it and read along with us.

On friday we talked about section 3.6 of the paper: subsurface patterns and properties. The real take-away message of this section is that Mars is layered. Everywhere that bedrock is exposed, it has layers. From the paper:

“On Earth, the observation of layers would not be a surprise, but the prevailing consensus … prior to the MGS mission held that much of the Martian crust, particularly in the ancient, heavily cratered highlands, should be something like that of the lunar highlands: an upper kilometer or two of interbedded crater ejecta, lava flows, and perhaps sediments and soils underlain by tens of kilometers of megabrecciated primordial crust…”

A great example of layering on Mars is the walls of Valles Marineris. The kilometers-high walls of this giant canyon show layers as much as 10 km below the surface! The authors point out that they had suspected that Mars was layered but they were really surprised by how deep the layers go!

moc_fig24

a) Layers in Valles Marineris; b) the box shows the extent of a, the arrows point to outcrops of light-toned layered material; c) & d) show other light-toned outcrops, and e) provides their context.

One especially interesting part of the Valles Marineris section was the observation that there aren’t very many boulders at the bottom of the cliffs. This implies that the rocks the walls are made of is breakable enough that large blocks can’t survive the violent tumble down the canyon walls. Thick volcanic rocks could easily survive such a fall, so the authors deduced that many of the layered outcrops are made of sedimentary rather than igneous rocks! That’s a pretty important conclusion based on an observation I wouldn’t even have thought of!

The paper points to other examples of sedimentary rocks elsewhere on the planet. In some cases, locations that were thought to be layered based on low-resolution images turned out to indeed be layered, but at a much finer scale. The large apparent layers were actually accumulations of dark sand, but where there was no sand, MOC revealed many small layers.

A spectacular example of layered sedimentary rocks in Arabia Terra on Mars.

A spectacular example of layered sedimentary rocks in Arabia Terra on Mars.

Based on the discovery of layers all over the planet, at depths up to ten kilometers, Malin and Edgett proposed a new model for the crust of Mars, depicted in this cartoon:

The new model for the martian surface as a "cratered" volume in which surfaces are constantly buried and re-exhumed while also undergoing impacts.

The new model for the martian surface as a "cratered volume" in which surfaces are constantly buried and re-exhumed while also undergoing impacts.

This model shows the surface of Mars as a very complicated place, constantly being buried and then uncovered, with craters interspersed throughout the sequence of layers. It’s a big contrast from the view of Mars as being essentially the same as the moon, with a  cratered surface and kilometers of crumbled up debris underneath. To support their new model, Malin and Edgett give some great examples:

Reull Vallis cuts right through the rim of a large impact crater. If the river had been flowing over a flat plain and encountered the crater, it should have been diverted. However, if the crater was buried, the river's course could pass right over it. Then as the landscape was eroded, the river could carve through the crater walls as they began to emerge. This is often seen on earth (e.g. the Susquehanna river cutting through the Appalachians) where mountains are lifted up and pre-existing rivers carve through them.

Reull Vallis cuts right through the rim of a large impact crater. If the river had been flowing over a flat plain and encountered the crater's rim sticking up, it should have been diverted. However, if the crater was buried, the river would not "see" it, and could pass right over it. Then, as the landscape was eroded, the river could carve through the crater walls as they began to emerge. This is often seen on earth (e.g. the Susquehanna river cutting through the Appalachians) where mountains are lifted up but pre-existing rivers maintain their original course by carving through them.

moc_fig33

Buried craters, ranging from completely filled (a), to partially exhumed (b,c) to almost completely uncovered, with only a small remnant of the fill remaining (d).

The authors point out that the constant burial and exposure of surfaces on Mars makes it very difficult to reliably tell the age of the surface by crater counting. A heavily cratered surface is certainly old, but it may have only been uncovered relatively recently. And how do you deal with a surface that accumulated some craters, was buried for a billion years, and then exposed, and hit by more impacts? Obviously, the new “cratered volume” idea of the martian surface in this paper poses some difficulties…

a) Context image showing a valley; b) a view of the valley wall. Notice that there are two craters that appear to be partially underneath the valley's layered wall. It is not obvious whether these are ancient craters that are being uncovered as teh valley erodes away the overyling layers, or whether they formed on teh valley floor and have been partially covered by debris falling off of the wall. These are shown in more detail in e. c and d show views of the upland and valley floor. It is impossible to tell whether the craters on the valley floor are old or young.

a) Context image showing a valley; b) a view of the valley wall. Notice that there are two craters that appear to be partially underneath the valley's layered wall. It is not obvious whether these are ancient craters that are being uncovered as teh valley erodes away the overyling layers, or whether they formed on teh valley floor and have been partially covered by debris falling off of the wall. These are shown in more detail in e. c and d show views of the upland and valley floor. It is impossible to tell whether the craters on the valley floor are old or young.

ResearchBlogging.orgMichael C. Malin, Kenneth S. Edgett (2001). Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruise through primary mission Journal of Geophysical Research, 106 (E10), 23429-23570 DOI: 10.1029/2000JE001455

New Google Mars

February 2, 2009

Google Earth’s latest edition was just released and guess what? It has a Mars setting! There was a way to overlay Mars data on the Earth globe in previous versions, but now that’s no longer necessary: just click a button and you’re on Mars. You can choose from a variety of global maps including topography, Viking images, Day and nighttime infrared, and visible color. It also has footprints for high resolution cameras like HiRISE, CTX, MOC, CRISM, and HRSC, with links to the full-resolution images. And most exciting, it has 3D topography! Now you can fly around in Valles Marineris or check out the view from Olympus mons.

The view from the edge of the Olympus Mons caldera in Google Mars.

The view from the edge of the Olympus Mons caldera in Google Mars.

Olympus Mons dominates the horizon in this Google Mars view.

Olympus Mons dominates the horizon in this Google Mars view.

Another way-cool feature is the ability to zoom into panoramas taken by rovers and landers, as shown here for Opportunity.

The Opportunity rover's traverse. Each camera icon is a panorama that you can zoom into.

The Opportunity rover's traverse. Each camera icon is a panorama that you can zoom into.

Part of the Rub al-Khali panorama taken by the opportunity rover.

Part of the Rub al-Khali panorama taken by the opportunity rover.

And finally, you can load selected Context Camera images right onto the globe, to take a high-res look at areas of interest, such as the Olympia Fossae troughs shown here. I don’t know what’ you’re waiting for: go download the program and try this out for yourself!

CTX image of the Olympia Fossae troughs.

CTX image of the Olympia Fossae troughs.

How to Look at Mars

August 20, 2008

There is so much Mars data out there that it hard to keep track of all of it! Thankfully there are some useful tools that let anyone look easily look at orbital data of anywhere on the planet.

The first is a program called “jmars“. This java-based program distributed by Arizona State University lets you overlay all sorts of global datasets, from MOLA topography to THEMIS nighttime infrared maps to H2O abundance from the Odyssey gamma ray spectrometer. It also shows the location of high-resolution images from MOC, HiRISE and CTX, and lets you either load a low-resolution version of the images right in jmars, or click a link and web-browse to a higher-resolution version. I use this program all the time. Here’s a screenshot of what I’m (supposed to be) working on right now. It shows a THEMIS day-IR map of the Meridiani region of Mars with CTX images overlaid on top and outlines of the locations of all the HiRISE (red) and MOC (pink) images of the area. (click for a bigger version)

I also discovered yesterday that you can generate a 3D view of Mars with jmars also! Check out this view of Valles Marineris (no vertical exaggeration).

The second tool that I often use is Google Earth. “But wait!” you say, “I thought we were talking about Mars!” Oh, we are. The trick is, you just drape earth in Mars data and everything works great! Here’s a link to a website describing how to set up Google earth to display all sorts of Mars data. Follow the directions and soon you too can click and zoom on a globe that looks like this:

Have fun!

Phoenix’s Neighborhood (Part I): The Basin

June 5, 2008

If you’re like us, you’ve been refreshing the Phoenix news page constantly, looking for the next update from Mars. If you need a little catching up on what’s going on in the mission, here are some recent posts with updates.

But with all the Phoenix coverage, there hasn’t been much talk about the context for the Phoenix landing site. What’s so cool about the north pole of Mars?

The north pole of Mars sits at the lowest elevation of the huge basin that takes up most of the northern hemisphere of Mars:


MOLA elevation map of Mars (credit: NASA)

Like any basin here on Earth, the northern basin acts as a trap for all kinds of materials from elsewhere on the planet: wind-blown sand, water and debris from outflows, groundwater, and maybe even precipitation. The idea that the northern basin may have once held water has made it the prime location for a possible ancient martian ocean.

While observations of features that look like shorelines and deltas support the concept of an ancient northern ocean on Mars, the evidence is not conclusive. Right now, the consensus in the scientific community is that the northern ocean may have never existed, and if it did, that it was pretty short-lived on geologic timescales.


Possible deltas and shorelines at the edge of the northern basin (Pablo and Pacifici, 2008).

Even if there never was an ocean, there has still been a huge amount of material deposited by wind and outflows in the northern basin. In the shaded elevation map above, did you notice how smooth the northern plains look compared to the southern highlands? This indicates that enough material has been added to the northern basin to smooth over and obscure the ancient cratered terrain – many, many kilometers of sediments.

The northern basin has gotten much more interesting in the past decade. Until high resolution images came back from Mars Global Surveyor in the late 90’s, it was thought that vast floods of lava had smoothed out the plains a few billion years ago, and not much had changed since. Our new picture of the northern plains is a vast stack of sediments that have been constantly reworked by erosion and permafrost processes for potentially billions of years.

In the next installment, we’ll look at the evidence for ice in the northern plains before Phoenix landed on it.