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Remote Sensing Missions to Mars

Since Mariner 9’s pioneering first mission to survey the surface of Mars, several have followed with more advanced equipment able to unveil more detail. This was in a bid to better understand the underlying processes that formed the features of the red planet, including aeolian structures such as sand dunes.

Mariner 9 Mission

Launched in 1971, the Mariner 9 mission had two primary objectives. Firstly, to map 70% of the Martian surface (originally the objective of the failed Mariner 8 mission) and to study temporal changes in the Martian atmosphere and surface. In terms of mapping, the mission exceeded expectations, managing to capture images of almost 100% of the surface. This revealed aeolian features and also large canyons, massive volcanoes and ancient riverbeds.

Despite this success, Mariner 9’s wide and narrow angle telescope cameras could only capture so much detail. The images created had at best a resolution of 1km, and with 5% of the surface this accuracy reduces to 100km. Although this is perfectly adequate to discover large geological features and entire aeolian systems, it is not detailed enough to study dunes in any great depth.

The Viking Missions

Viking Orbiter image of  Martian surface sand dunes (nasa.gov)

Viking Orbiter image of
Martian surface sand dunes (nasa.gov)

NASA’s Viking Mission to Mars was composed of two spacecraft, Viking 1 and Viking 2, each consisting of an Orbiter and a lander. The mission objectives were to capture high-resolution images of the Martian surface, characterise the structure of the atmosphere and surface, and finally to search for signs of life. Launched in 1975, Viking 1 and 2 Orbiter spacecraft orbited Mars at a distance of 300km above the surface for 1400 and 700 rotations respectively, returning images of the entire surface of Mars with a resolution of 150 to 300m. At selected points of interest, this resolution was improved to an impressive 8m.

The results from Viking gave us the most complete view of the Martian surface to date. The Orbiter images confirmed the existence of volcanoes’, canyons and aeolian features as well as discovering large cratered regions and even evidence of surface water once existing. It meant that these features could be studied in greater detail, and specific regions of sand dunes and sand dune types were discovered.

Mars Global Surveyor (MGS)

MOC image of  Martian north polar sand dunes (nasa.gov)

MOC image of
Martian north polar sand dunes (nasa.gov)

Launched in 1996, the Mars Global Surveyor spacecraft was NASA’s first mission to Mars in 20 years. It is still the longest serving mission to date, successfully observing the surface for over nine years until November 2006. It was designed to circle in a polar orbit around the planet (travelling over one pole to the other) twelve times a day collecting images from a height of 400km.

The aim of the mission was to contribute to the four main goals of Martian exploration at the time: determine whether life ever existed on Mars, characterise the climate of Mars, characterise the geology of Mars and prepare for human exploration.

To help achieve this, the surveyor spacecraft was fitted with some of the most advanced instrumentation ever sent into space. Part of this payload was the Mars Orbiter Camera (MOC). This camera had two functions; firstly to take a daily wide-angle image of Mars, similar to the weather photographs seen of Earth, in order to study the climate, and secondly to take narrow-angle images to better understand the geological features.

As with the previous two Martian missions, the Global Surveyor was a great success. The landmark discovery was to be the existence of gullies and debris flow features, suggesting that there could be current sources of liquid water on or near the surface of the planet. This wasn’t to be its only achievement however, as it returned images of the surface down to a resolution of 0.5m. The most detailed so far, they provided new information about the physical nature of the windblown material on the Martian surface and showed that the pre-MGS view was much too simple. In addition to bright dust and dark sand, MOC images show evidence of bright sediment that can be transported by saltation (e.g., sand) and dark material that can be transported in suspension.

Mars Odyssey Mission

THEMIS Image of Bunge Crater Dunes

THEMIS Image of Bunge Crater Dunes

Part of NASA’s ongoing Mars Exploration Program, the Mars Odyssey spacecraft launched in 2001, and is still observing the planet to this day. As with MGS, its aim again is to contribute to the four main goals of exploration, and to do this five mission objectives have been derived: to globally map the elemental composition of the surface, determine the abundance of hydrogen, to acquire high spatial and spectral resolution images of mineralogy, provide information on the morphology of the surface and to characterise the radiation risk to human explorers.

The Odyssey spacecraft was fitted with three main instruments to help achieve its targets. THEMIS (Thermal Emission Imaging System) is a camera used to identify the mineralogy of the planet, by studying the different heat radiation properties present. GRS (Gamma Ray Spectrometer) for determining the presence of 20 chemical elements on the surface including hydrogen, and finally MARIE (Mars Radiation Environment Experiment) for studying the levels of radiation present.

Although at first glance none of these instruments seem suitable for the study of aeolian features such as sand dunes, the THEMIS camera also surveys the surface through the visible spectrum. The resulting images have a resolution of 18m, and to date the camera has taken over 15,000 20x20km shots. This resolution nicely ‘fills the gap’ between the large-scale images of the Mariner and Viking missions and the very-high resolution images of the MGS instrumentation.

Mars Reconnaissance Orbiter (MRO)

HiRISE Image of Polar Dunes (University of Arizona, 2011)

HiRISE Image of Polar Dunes (University of Arizona, 2011)

Launched from Cape Canaveral in 2005, the Reconnaissance Orbiter’s main objective is to search for evidence that water persisted on the surface for a length of time. While previous missions have shown that water flowed across the surface, it remains a mystery whether water ever existed long enough to support life.

The MRO spacecraft is one of the most comprehensive missions ever sent to Mars, with a payload of many different types of instrumentation. As well as the numerous spectrometers, radiometers, radars and engineering instruments on board, three cameras have been included to fulfil a variety of objectives. MARCI (Mars Colour Imager) takes large-scale images of the planets atmosphere in order to study clouds and weather patterns. Two other cameras, HiRISE (High Resolution Imaging Science Experiment) and CTX (Context Camera), are able to take images of a much more suitable resolution to study aeolian features in detail.

HiRISE, as the name suggests, takes ultra-high resolution images of the Martian surface in order to reveal details of the geologic structure of canyons, craters and aeolian features. Able to produce results at a 0.5m resolution, it has so far returned some of the most detailed and striking images of the Martian surface ever captured.

CTX was designed to be used in conjunction with HiRISE, providing wide-area views of the areas being studied in order to provide a context for the high-resolution analysis of key areas of the surface. Although predominantly an auxiliary instrument, CTX produces good quality images in its own right, and has currently returned data for over 50% of the planet at a resolution of 6m. Although not matching the detail of HiRISE, they still can still be used to study sand dunes in detail while having a much-improved field of view.

If you have any other questions regarding some of the things you have spotted on Planet Four: Craters, please feel free to ask on Talk, and in the mean time please keep marking on craters.planetfour.org!

The Cerberus Fossae

The focus of this post will be on the area of the Martian surface that Planet Four: Craters volunteers have been marking craters on, the Cerberus Fossae.

The Cerberus Fossae is a set of west-north-west trending and almost parallel fissures or fractures that cut across the Cerberus plains on Mars. Evidence suggests that the fissures have been formed by faults that pulled the crust apart in the Cerberus region (9°N, 197°W).

Ripples seen at the bottom of the fault are sand blown by the wind. The underlying cause for the faulting was believed to be magma pressure related to the formation of the Elysium volcanic field, located to the northwest. The faults pass through pre-existing features such as hills, indicating that they are a young feature by the standards of those found on the surface.

In fact, this area of Mars has been identified as having the youngest volcanic plains on Mars. Early crater-counting efforts have suggested that the youngest lava surfaces in the area are less than 10 million years old. This is why it is of such interest to future missions to Mars, as a location where seismic activity might still be happening. To help predict the amount of seismic activity to expect, we need your crater markings to make a more accurate estimate of the age of the region.

If you have any other questions regarding some of the things you have spotted on Planet Four: Craters, please feel free to ask on Talk, and in the mean time please keep marking on craters.planetfour.org!

James

Crater Features

Since the launch of Planet Four: Craters a few weeks back, we have had several Talk posts regarding different features and markings that have been spotted in and around the craters themselves. This post will go through what some of these markings might be, and hopefully answer some of the questions you have had!

Recurring Slope Lineae (RSL)

RSL

Recurring slope lineae are narrow, dark markings found on steep slopes (like crater edges) that incrementally lengthen during warmer periods, then fade over cooler seasons and can recur over multiple Martian years. They can grow to be several hundred metres in length, and it has been suggested that they are caused by wet flow – originating from melted ice.

Active Gullies

gullies

Martian gullies are small networks of narrow channels, along with their associated down slope deposits, that occur on steep slopes, especially on crater walls. It has been suggested that they are formed by a flow of dry material, supported by a layer of dry ice just below the surface.

New Impacts

new impact

As the name suggests, these are craters that have been formed by impacts that have occurred in the near past. They are found all over the surface of Mars, and although they vary in size the smaller ones are much more frequent. They can be spotted by the darker coloured ejecta formed around them (due to the disturbed surface material that has yet to settle), or in some cases the presence of brighter patches – indicating where subterranean ice has been revealed.

If you have any other questions regarding some of the things you have spotted on Planet Four: Craters, please feel free to ask on Talk, and in the mean time please keep marking on craters.planetfour.org!

James

Calling All Undergrads: Spend A Summer Working on Planet Four in Taiwan

poster2015e

I’m a postdoctoral fellow at the Institute of Astronomy & Astrophysics at Academia Sinica (ASIAA)  in a Taipei, Taiwan. As part of the 2015 ASIAA Summer Student Program, we’re looking for an undergraduate student to come to Taipei for the summer, from July 1st-August 28th, to work on Planet Four related research.

Last year, Chuhong Mai participated in the program and helped get the map project information we need to make the final catalogs for the first Planet Four paper. As a result of her efforts last summer, Chuhong is going to be co-author on the paper. You can learn more about her experience at ASIAA and as part of the summer program here.

ASIAA operates in English, and all research will be conducted in English.  The description of this year’s project can be found here. The aim will be help develop tools to look at wind directions based on the Planet Four fan markings for one of the HiRISE targeted regions  (likely Inca City or Manhattan) and see how fan directions change from year to year. Details about the Summer Student Program including rules and restrictions can be found here.

Applications are due before March 20th. If you have questions or if you would  like to know more, you can contact me via email at  mschwamb AT asiaa.sinica.edu.tw

Using Tag Groups to Collect Images on Talk

More on making tagged group collections from the Darren on the Zooniverse blog

Zooniverse

Hashtags are an important element of how the current generation of Zooniverse’s Talk discussion system* helps to power citizen science. By adding hashtags to the short comments left directly on classification objects, users can help each other (and the science teams) find certain types of objects—for instance, a #leopard on Snapshot Serengeti, #frost on Planet Four, or a #curved-band on Cyclone Center. (As on Twitter, hashtags on Talk are generated using the # symbol.)

One of the ways in which zooites can take advantage of hashtags is by using Talk’s tag group feature. A tag group (also called a “keyword collection”) is a collection that automatically populates with all of the objects that have been given a specific hashtag by a volunteer.

For instance, here is a Galaxy Zoo tag group that populates with all Galaxy Zoo objects that have been tagged #starforming. It will continue to automatically add new…

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The Sun is back!

 I wrote a post on my new blog showing how I go about finding out what’s currently going on at the southpole of Mars!
Sorry for the cross-linking, but there’s no way to show the nice IPython notebooks (combing text and code) in a clear and pretty format here in WordPress:

Animated markings

After the first day of our currently ongoing workshop for Citizen Science I have reached my personal goal for the day and created a tool to display an animated version for all the marked blotches of a PlanetFour image.

Here’s the result:

More to come in the upcoming days.

Dry ice snowfall

About a week ago our colleague and a resident polar scientist on the Mars Climate Sounder (MCS) science team Dr. Paul Hayne wrote this Planetary society blog post. He talks about CO2 snowing on Mars! If you are interested to know why we think that it snows dry ice on Mars or what shape CO2 snowflakes are, go check it out! And let us know your thoughts on how it affects the areas that you are helping us to analyze!

Anya

New Link for the Live Chat

Some technical difficulties but we are live

 

Standing on the Surface

With the HiRISE images we show on Planet Four, you’re peering down at the Martian surface from above, seeing the fans and blotches that we want you to you mark.  What would something like the image below  look like from the ground if you were standing on the thawing carbon dioxide ice sheet during the Southern spring?

50e741ba5e2ed2124000379f

Well, if the geysers were actively lofting carbon dioxide gas and dust and dirt from below the ice cap up onto the surface and into the Martian air, you’d probably see something like the artist’s conception below.

Image credit; Arizona State University/Ron Miller

Artist’s rendition of geysers on the South Pole of Mars – Image credit; Arizona State University/Ron Miller

How high are the plumes? Current estimates suggest that the geysers and material it lofts stay relatively close to the ground going probably no higher than about 50-100m into the air according to previous estimates based on fan length and simple deposition models. Though more likely, the geysers achieve smaller heights than that most of the time. To try and directly measure the geyser plume heights, stereo imaging where Mars Reconnaissance Orbiter pointed at the same spot twice at different look angles has been used. The two resulting HiRISE images are then combined to give height information in much the same way our brains combine the  images obtained from our eyes, each viewing at a slightly different angle and position than the other, to get depth perception. HiRISE would have been able to see the geyser plumes above the ground in the combined stereo pairs,  if the majority achieved heights of 50-100 m, but no image to date yet has caught a detection of a plume. So that suggests that the geysers may not reach these maximum heights but instead only go up to maybe 5-10m off the ground.

Your clicks may be able to help constrain better the height of the geyser plumes. With your classifications, we will have the largest sample of fan lengths and directions and blotch radii ever measured on the Martian South Pole. With the fan lengths from your markings,  a measure of the terrain’s slope, and an assumption for the particle size of the Martian dirt/dust being entrained by the escaping carbon dioxide gas, you can estimate the maximum height needed to loft the material for it to fall at a given distance from the geyser for a range of wind speeds.