Lunar Prospector

Lunar Prospector crashing into the south Lunar Pole.

Lunar Prospector is nearing the completion of its full 18 month primary and extended missions. Many new insights into lunar science have resulted. As the spacecraft nears the end of its useful lifetime, a bold experiment will make a final attempt to glean a last nugget of science from an already successful mission. A team of scientists led by David Golstein of the University of Texas will endeavor to smash the tiny spacecraft into a permanently shadowed south pole crater. If all goes well in this low probability, high pay-off attempt, a direct signal of water ice could be viewed by land and spacebased telescopes. The crash time is 0951 UTC on July 31.

List of Frequently Asked Questions

about the Lunar Prospector impact on the Moon:

Is there a website to get more information about the Lunar Prospector mission?

A Lunar Prospector webpage exists at

From there is a link to the Lunar Prospector Impact Page at is a picture of the impact site is the crash crater location is another Lunar Prospector web page

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What Time will the Impact Occur?

July 31 at 0951 UTC (that's 2:51 am Pacific, 5:51 Eastern)

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Where will the spacecraft crash?

The Prospector will crash into a permanently shadowed crater on the Lunar south pole. The crater is named Mawson. It is near the south Pole of the moon, an area in permanent shadow. Although the Lunar Prospector spacecraft will weigh only 354 pounds (161 kilograms) at mission end, the energy at impact will be the equivalent of crashing a two-ton car at more than 1,100 miles per hour.

The current plan calls for a controlled impact of the Lunar Prospector spacecraft in the early morning hours of July 31 directly into a small crater (Mawson), located at the southern lunar pole. This crater is ideal for the proposed experiment. It is only 31 to 38 miles (50 to 60 kilometers) across and has a rim which is high enough to provide a permanent shadow, yet it is low enough to provide for a suitable spacecraft impact trajectory. Data from other observations suggest that the crater could contain a high concentration of water ice. Finally, the crater is observable at impact time from Earth-based observatories and orbiting platforms.

Much of the area around the south pole is within the South Pole-Aitken Basin (shown at left in blue on a lunar topography image), a giant impact crater 2500 km (1550 miles) in diameter and 12 km deep at its lowest point. Many smaller craters exist on the floor of this basin. Since they are down in this basin, the floors of many of these craters are never exposed to sunlight.

"The argument for targeting [the Mawson] crater is that it is both in permanent shadow, as shown by our radar data, and also has a high hydrogen abundance, as shown by new Lunar Prospector data. This makes it a prime candidate for water ice deposits."

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Will amateur astronomers be able to see the crash?

Amateurs will be pointing their telescopes at the moon on the morning of July 31. What they will see of the crash and water ice (hopefully) is unknown. But the moon will make a beautiful target to view on the morning of July 31.

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Will any Amateur Astronomers be looking at the moon on this night?

The Observatory at Fremont Peak State park will be manned by FPOA members on the night of July 30 and the morning of July 31 (by Morris Jones and Jane Houston) and they will be attempting to view the crash with the aid of the 30 inch "Challenger", and their own 17.5 inch Reflector telescopes. A map to Fremont Peak can be found here:

Contact other clubs by visiting the AANC club listing to see if other local clubs have plans on this night.

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Is the Crater Mawson shown on moon maps?

Not any that we've found so far. The Atlas of the Moon by Antonin Rukl, published by Kalmbach Books has some pages that show the south pole of the moon. Look on charts 73 and 74 (on pages 172 to 175) which show the south pole region. Then go to page 186 for the chart of libration zone V, south-southeast sector of the moon. The 1/3 semi circle (unnamed and featureless) and near crater Malapert is crater Mawson (I think!) - it looks like it when compared to the photos on the web pages above.

Map 14 and Plate 14A in the book "the Hatfield Photographic Lunar Atlas" shows the craters Amundson, Scott and Malapert. This is pretty much the area to look.

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Is there a web site for the Rukl Atlas of the Moon atlas charts?

Yes, thru the "Hitchhikers Guide to the Moon" website you can get to which gives you an index to lunar features by numbered Rukl chart. - the front page of the website has a map of the moon with each RUKL page identified. Here's a shortcut to the online Rukl pages:

Chart 73

Chart 74

There is no online libration chart V.

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What's up on the Moon on July 31 (and the 30th and August 1)?

The gibbous Moon will be visible during the late evening and through to dawn, and will transit during the last hours of darkness. At the midpoint of the terminator (The boundary between the illuminated part of the Moon's disc and the dark part is called the terminator. At the time of the quarter moon, it is essentially a straight line running north-south). On the 30th, Just above the midpoint of the terminator, the last remnant of the Mare Crisium appears as a smooth bite taken out of the Moon's edge.

The eastern edge of the Mare Tranquillitatis will be overtaken by darkness on the 31st and more than half in darkness on the 1st. To the north of it, the rough oval of the Mare Serenitatis is still complete. At their junction, crater Pliny stands out well against the smooth darkness around it. At the north-east edge of Serenitatis, the larger Posidonius shows as a bright ring.

To the south of Posidonius, and north-east of Pliny, the Sun will set tonight on the landing site of Apollo 17, where in 1972 Eugene Cernan and Harrison Schmitt became the last men to set foot on the Moon. And as the Lunar Prospector crashes into the moon on this night, it carries a special cargo. The ashes of planetary geologist and comet co-discoverer Eugene Shoemaker are aboard the Prospector. Gene trained the Apollo astronauts, studied impact craters on earth and the moon, and was the first to propose water on the moon - ironically, the mission of the scrappy Lunar Prospector. I'll be looking at the moon on this night to bid farwell to this human lunar prospector who finally made it to the moon.

See this website for day to day descriptions.

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I want to learn more about the Moon! Where can I see it with local astronomy groups?

Those interested in lunar observing in San Francisco can attend the San Francisco Amateur Astronomers (SFAA) monthly "City Star Party". Held at the GGNRA site at Camino Del Mar and Point Lobos Avenues in San Francisco on the Saturday nearest the first quarter moon. Or join the Sidewalk Astronomers at 24th between Sanchez and Noe or at Ninth and Irving in SF on the First Quarter Moon Saturday night also. The next first quarter moon Saturday nights are July 17, August 21 and September 18.

The SFAA Hotline is (415) 566-2357 . The Sidewalk Astronomers Hotline is (415) 289-2007.

For a complete list of Northern California Amateur Astronomy clubs, phone numbers, websites and star party dates visit the AANC Website at:

The Lawrence Hall of Science (LHS) offers Saturday Night Stargazing every clear Saturday night on the Lawrence Hall of Science Plaza. See the moon, planets, star clusters, galaxies, and more through astronomical telescopes on Saturdays from 8pm-11pm on the Lawrence Hall of Science plaza (weather permitting). Saturday Night Stargazing is a free public viewing program sponsored by the LHS Holt Planetarium and Bay area amateur astronomers.To find out more about celestial events, call (510) 642-5132, press 1, and then press 7.

The San Jose Astronomical Association holds in city star parties at Hogue Park in Campbell on the first quarter moon Friday nights, weather permitting. Other monthly star parties, astronomy classes, general meetings with interesting speakers and much more are offered and listed on the club website at Directions to the observing sites are on the website too. Or call the hotline (408) 559-1221 for current events.

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Are there websites where I can go to find out more about the Moon?

An easy mooning article - what's up during the month:

"A Day in the life of the Moon" by Jane Houston is at

The best of the Solar System websites!!

Bill Artnett's "The Nine Planets"

Everything you need to know about the Moon and more!! Akkana Peck's "The Hitchhiker's Guide to the Moon" is at

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Compiled by Jane Houston ( on July 9, 1999