Q. Do I need to be a scientist to participate in this project?
A. Absolutely not. The whole idea is to see if non-scientists can help with the 95% of the task that requires only basic human abilities like recognizing pictures. If you know a mountain from a hole in the ground, you can be a crater-marking clickworker. Crater classification is a little more subtle, but may also be a task that ordinary people can do. Give it a try.
Q. Will each image be done by only one person (clickworker), or will you be cross-checking several people’s answers?
A. We are giving the same images to different clickworkers, and in the future we will cross-check their answers. We will probably tell you the quality of your results once that software is written.
Q. Some craters are hard to assign to one of the three classes. How about more classes? How about classes for smooth vs. chunky ejecta, or splashy vs. pancake?
A. We're currently [January 2000] working on adding an Advanced Crater Classification activity. That will ask you to classify the ejecta stratigraphy (layers), ejecta morphology (shape), and interior morphology, according to the same scheme used by the geologist who did the current crater catalog.
Q. Can I name a crater?
A. Hundreds of craters on Mars already have names, but most probably never will. Official names are assigned by the International Astronomical Union.
A. If the problem goes away after a reload (you may need to clear your cache), it may be due to the connection being dropped before the script was fully loaded. If the problem persists, it is most likely due to a browser incompatibility. The crater-marking activity uses the new Document Object Model standard, which is supported by Mozilla-based browsers such as Netscape 6. It also works with one non-standard browser: Internet Explorer (both Windows and MacOS versions). Crater classification works in Netscape 4.7, at least, as well as the above browsers.
Q. Is it possible to get the color of the crater-marking crosshair cursor to change? On some pictures it is very hard to see where it is.
A. Not automatically, because the relevant web standard (CSS2) does not provide a way to do that. Suggestion: wave the mouse around a little; it's easier to see a moving object. Reportedly, the cursor is under individual user controller for Windows IE users: Go to your Control Panel (Start | Settings | Control Panel|), click on the Mouse icon, then the Pointers Tab, then then Precision Select option, and set it to whatever graphic you like.
Q. Is this a big NASA project?
A. No, it's a tiny little NASA project. The web site and database were created and are being maintained by one engineer working part-tme, advised by two scientists who spend even less time on the project. It's a pilot study sponsored by the NASA Ames Director's Discretionary Fund. Depending on what we learn from this, it's possible that more ambitious projects along these lines will be attempted, once we know the idea works.
Q. How many of my tax dollars are paying for this?
A. Not a penny (much less than a penny). This study costs the average American household about one tenth of one cent, spread over two years. In the future, Mars missions, which these days cost $3 to $5 per household, could probably afford a data analysis project many times this size. In fact, it could save taxpayer money if volunteers can help with the data analysis.
Q. I marked (or classified) a lot of craters awhile back, but when I came back to the site, it had forgotten them.
A. It still remembers the work you did, but it doesn't remember who did it. Your identity is tracked with a cookie: a meaningless number that your browser repeats to the server whenever you return to the site. It expires after 90 days, but if you come back to the site at least once a month, it gets renewed whenever it's within 30 days of expiring. If you have cookies disabled, it will forget you right away, unless you bookmark a URL that has your clickworker id in it.
Q. Can you add a username and password login facility so I can login from different machines and my totals will be combined?
A. This isn't available yet, and adding it implies a lot of complications, such as a forgot-my-password service. For now, you can email yourself a URL from one machine that has clickworker=xxxxxxxxxxxx in it, and use that as a bookmark on the other machine.
Q. How big is the image I’m looking at?
A. Either 60km or 237km (37 or 148 miles).
Q. I’d be curious to see which part of Mars I’m looking at.
A. This is a low priority feature to add, because it doesn't help the science and may even hurt it a little. It's like double-blind clinical studies -- the doctors and patients might be curious about who is getting the real drug and who is getting the placebo, but the results are more trustworthy if no one knows until afterward.
Q. Why isn’t my ’quality estimate’ in the upper right ever getting updated?
A. There turned out to be too many clickworkers for the algorithm I wrote (to compare them to each other) to keep up in real time. I'd have to rewrite it, and I'm not sure that would be the best use of the small amount of time I still have to spend on the project.
Q. Are there automatic image recognition algorithms that could do crater recognition?
A. There have been several attempts, with limited success. If the process is ever automated and scientists come to trust computer vision as much as human vision, then there would be no more need for clickworkers to mark craters. There will still be other visual tasks that humans can do better than computers. Crater marking and classification are just the first test cases.
Q. What is the main purpose of this site?
A. The first stage of this pilot project is only trying to answer some meta-science questions:
Q. What scientific questions can be answered? What does a circle around a crater tell a scientist?
A. Circling a crater tells us that there’s a crater of a certain size at a certain location. Assigning a crater to a class based on its shape (morphology) tells us even more. The statistics gathered from that have been used to answer many questions about Mars (and other planets with solid surfaces, and moons). Here are some examples of questions already partially answered about Mars:
- How long has the Martian surface remained unchanged, compared to Earth and other planets and moons?
- By assuming that meteor impacts that cause craters happen at a constant rate but are then eroded away, we can estimate how much resurfacing a world has. Earth’s craters disappear quickly (in thousands or millions of years, whereas its moon, now that its volcanoes are gone, has nothing to erode craters except for smaller meteors. The data from Viking Orbiter data suggests that some Mars surfaces hardly change over billions of years, much longer than on stormy Earth, icy Europa, or volcanic Io. New MGS data shows that the surface is changing all the time at a finer scale, but no systematic crater count has been done yet. Perhaps you’ll get to help with that question.
- How recently were different parts of Mars resurfaced by flooding, weather, etc.?
- A small crater in the middle of a flood plain, like the ones in Ares Vallis near the Pathfinder landing site, must have been emplaced after the flood. Counting them gives an relative idea of when the flood occurred. Water rings in a crater, as seen in the crater within Gusev crater, suggest that the crater contained a lake sometime after it was formed. The relative geologic ages on Mars, like on Earth, have names (Noachian, Hesperian, Amazonian in the case of Mars.). On Earth, scientists eventually were able to assignabsolute dates to those ages, but craters only only give relative ages.There’s an excellent essay you can read for a more detailed explanation and illustrations. One striking thing about Mars is that the southern hemisphere’s surface is much more ancient (heavily cratered) than the northern hemisphere’s, as illustrated here.
- What kinds of asteroids and comets have hit Mars, Earth, and other planets throughout the history of the Solar System?
- The study of how many craters of certain sizes have been produced at different time periods tells us that there have been different sources of impacting material. On Earth, weather and continental drift erase the evidence.
- Is there still water on Mars, lurking beneath the surface? Where, and how deep?
- The distribution and characteristics of different ejecta morphologies (the shape of the blanket of material thrown around the crater by the impact) across the planet has been used to chart the depth and location of subsurface water and ice.
- Can we tell what the surface of Mars is like from orbit, in the places that spacecraft have not yet landed?
- The relationship between interior features and crater size and location has been used to study the effects of surface properties on the formation of certain interior features.
- Did Mars ever have weather, or flowing water?
- The degree of degradation of impact craters in different regions has been used to study the erosional history of Mars.
- Where is the best place to send future landers if we want to look for evidence of extinct Martian life?
- Craters which appear to contain sediments from ancient lakes have been studied as potential landing sites for future sample return missions.
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