When "Bill Nye the Science Guy" went on the air in 1993, one of the smartest smartphones around was an $899 brick-sized contraption called the Simon Personal Communicator. Today, Simon is ancient history — but Bill Nye's smarts are still circulating, on video, on the Web, and now on the latest generation of smartphones and tablets.

The Bill Nye the Science Guy app — introduced this month by Disney for iPhone, iPod Touch and iPad — celebrates the 20th anniversary of Nye's premiere by offering clips from some of his shows, a gaggle of games with space and science themes, a virtual Martian sundial, six experiments to do at home, and even instructions for tying his signature bow tie.

It's been a long, strange trip for the former Boeing engineer, who first struck a chord on TV with a mad-scientist gig on Seattle radio and TV stations. That led to the children's show that bore his name, followed by a science show for grownups called "The Eyes of Nye," followed by his service as the nonprofit Planetary Society's chief executive officer. Today, he has the kind of science celebrity status that Mr. Wizard, a.k.a. Don Herbert, had for an earlier generation.

Nye, 57, says he's honored by the comparisons to Mr. Wizard.

"Don Herbert, Mr. Wizard, sent mankind to the moon," Nye told NBC News. "Many of the young engineers who went to work at NASA in the 1960s were inspired by Mr. Wizard in the 1950s. I studied Mr. Wizard episodes. ... If I'm really carrying the torch of Don Herbert, that's a pretty worthy life right there."

Disney

Bill Nye's 20th-anniversary app provides clickable links to games, experiments, video clips and gewgaws.

Nye isn't shy about getting involved in the controversies that surround science and society — which is something Mr. Wizard hardly ever did. Whether it's defending the scientific community from congressional critics, debating climate deniers or dressing down Darwin's detractors, you can rely on Nye to be on the front lines. 

"I say to the grownups, if you want to deny evolution and live in your world, in your world that's completely inconsistent with everything we observe in the universe, that's fine," Nye said last year in a widely watched BigThink video. "But don't make your kids do it, because we need them. We need scientifically literate voters and taxpayers for the future."

In an interview scheduled to promote the release of his app, Nye reflected on topics ranging from the future of the space effort to those crazy bow ties:

On the show's longevity:
"It's just amazing to me that 20 years later, people are still using the show in classrooms. The show still has value. I went to see Carl Sagan [the late astronomer who was one of Nye's professors at Cornell], and he said, 'Focus on pure science. Don't mess with technology. Kids resonate pure science.' It was good advice."

On the keys to better education in science, technology, engineering and math (STEM):
"What I believe right now, based on a very compelling study done at Michigan State University by Jon Miller, is that algebra is the turning point. The single biggest indicator for whether or not a person will pursue a career in math, science or engineering is not science education per se. It's actually algebra. So I believe that algebra is not expensive to teach. We just have to adjust our curriculum a little bit, so that people are using symbols to represent numbers earlier in their school career."

On experiments he hasn't done that he still wants to do:
"I like blowing things up, but that's not my main thing. Anytime you get something falling a long way or shooting up a long way, that's pretty good. Who doesn't want to build his own rocket? One thing that does interest me, I gotta say, there's Virgin Galactic and there's a company called XCOR with the Lynx rocket plane. ... That really intrigues me, going into space for a few minutes."

On the future of the space effort:
"What we advocate is $1.5 billion for planetary science, and the other thing we advocate is the Decadal Survey. The Decadal Survey was produced by the National Research Council. They got scientists and engineers together, and they met and they met and they met for two years, and they argued, and they said, 'Here's what we want to do: We want to bring back a sample from Mars, and we want a mission to Europa.' ... Human spaceflight does not have the equivalent of a Decadal Survey. In my opinion, that's their problem. In human spaceflight, you've got to be thinking about decades, not a single decade. It is a hard, hard business."

On the reason why Mars is the main target of space exploration:
"What we want to do is get a person to Mars for the sake of exploration, because there are two questions that get everybody: Where did we come from? And are we alone? If you say you don't ask those questions, I don't believe you. To answer those questions, you've got to explore space, and the next logical place to look for life is Mars. You could say it's Europa, and we say yes, yes, yes, the Planetary Society is kooky for Europa. We want to put a boat on Titan. Yes, cool. But humans on Mars has got to be the goal, and there has to be something equivalent to the Decadal Survey. We have to get people in Congress, and the Office of Management and Budget, and NASA ... Everybody's got to get together and not get off on 'Let's land on the moon,' or 'Let's drag an asteroid beyond the moon.'

On the origin of Bill Nye's bow-tie fashion statement:
"When I was in high school, by long tradition, the boys wait on the girls at the girls' athletic banquet. ... So I said to my colleagues, 'OK, guys, if we're going to be waiters, let's really dress like waiters. Let's impress the ladies.' So my father, who's very skilled with knots, showed me how to tie a bow tie. And I got ... well, I won't say obsessed, but I became quite interested in bow ties. I remember practicing tying the tie over and over again around my leg — your thigh is about the same diameter as your neck, at least for most people. It became a thing. I have several hundred bow ties now. The Smithsonian — the Smith-freakin'-sonian — wants my ties."

More about Bill Nye the Science Guy:

• Video: Space debate sparks Bill Nye's wrestling move
• Bill Nye helps bird physics game take flight
• Bill Nye issues warning on creationism

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

NASA / JPL-Caltech / MSSS

You can spin and zoom in on a 360-degree panorama of the Curiosity rover's surroundings at Rocknest on Mars, thanks to an interactive Photosynth viewer. A guided tour points you to some of the hot spots. Click on the image to go to the viewer, or try out the embedded version below.

Fans of extraterrestrial anomalies will have a field day with the billion-pixel view of the Curiosity rover's surroundings at a place called Rocknest on Mars. The 360-degree clickable panorama lets you zoom in on an eerie Martian "bird," a weird series of holes, or a shiny object sitting on the Red Planet's surface.

Never mind that all these anomalies are perfectly explainable: It's a weird and wonderful way to take in all the sights that the rover has been seeing, from the pebbles in front of its own wheels to the slopes of faraway Mount Sharp.

"It gives a sense of place and really shows off the cameras' capabilities," Bob Deen of the Multi-Mission Image Processing Laboratory at NASA's Jet Propulsion Laboratory said in a news release about the interactive image. "You can see the context and also zoom in to see very fine details."

Deen assembled the 1.3-billion-pixel zoomable mosaic using 850 frames from the telephoto camera of Curiosity's MastCam instrument, supplemented with 21 frames from MastCam's wider-angle camera and 25 black-and-white frames — mostly of the rover itself — from the NavCam system. The images were taken on several different Mars days between Oct. 5 and Nov. 16, 2012.

This isn't the first billion-pixel pic from Curiosity: Russian photographer Andrew Bodrov assembled 407 frames from MastCam's cameras to create a 360-degree, 4-billion-pixel Martian panorama, as seen in December and January from a vantage point known as "Grandma's House."

The cool thing about JPL's panorama is that you can click right into some of the main attractions — ranging from a bird-shaped rock, to the holes left behind by Curiosity's laser-blasting ChemCam instrument, to a shiny scrap of material that apparently fell off the spacecraft. Give it a look, either by going to JPL's website, checking out GigaPan's gallery, or trying out the embedded version below.

More about Mars:

• Martian 'rat' takes Internet by storm
• This is how a lone rock rolls on Mars
• Cosmic Log archive on Mars

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

NASA

NASA contemplated setting up a lunar outpost like the one shown in this artwork back in 2007. Now House Republicans are reviving the idea of establishing a "sustained human presence" on the moon and Mars.

House Republican leaders want to push for outposts on the moon and Mars — and they want to push NASA's plan to snare an asteroid into the dustbin, according to a discussion draft of their space spending plan.

"It is the policy of the United States that the development of capabilities and technologies necessary for human missions to lunar orbit, the surface of the moon, the surface of Mars, and beyond shall be the goals of the administration's human space flight program," the GOP version of the NASA authorization bill states.

One of the goals would be "to develop a sustained human presence on the moon and Mars," according to the draft, which is expected to come under discussion at a House Science space subcommittee hearing on Wednesday. NBC News received a copy of the draft in advance — as did several other media outlets, including Politico and Space News.

Axing the asteroid mission
The draft bill would block the Obama administration's initiative to send a robotic probe to a near-Earth asteroid in 2017, with the aim of bringing back the space rock — or a substantial piece of it — for study by astronauts in the vicinity of the moon around 2021. On Tuesday, NASA touted the plan as part of an initiative that also includes a stepped-up program to identify potentially threatening asteroids and figure out what to do about them.

During a recent round of hearings, congressional Republicans were supportive of the asteroid-hunting effort, but sharply critical of the asteroid-grabbing mission. That's reflected in the draft legislation.

The draft would hold NASA's spending level at $16.9 billion, in accordance with the current sequestration situation, but it leaves the way open for increased funding if a deal is struck to loosen the budgetary purse strings. It would continue to fund NASA's major development projects, including the Orion crew capsule, the heavy-lift rocket known as the Space Launch System, and the James Webb Space Telescope. It also sets aside $700 million for supporting the development of crew-capable commercial spaceships — which is less than the administration's budget request of more than $820 million.

Debate over moon and Mars
The main point of debate is likely to be the thumbs-up for outposts on the moon and Mars, and the thumbs-down for the asteroid mission that has become the Obama administration's main focus for space exploration. NASA has said such a mission would help clear the way for exploration of Mars and its moons in the mid-2030s.

The idea of establishing a lunar base arguably played a role in the decline of former House Speaker Newt Gingrich's fortunes in the 2012 presidential campaign. Gingrich's plan to have a moon base in operation by 2020 drew derision from Mitt Romney, who said he'd fire any employee who suggested spending hundreds of billions of dollars on such a venture.

Estimates for the cost of building a moon base have run from $40 billion to $500 billion, depending on whether the person doing the estimating wants to encourage or discourage the idea. In comparison, estimates for the total marginal cost of the asteroid redirect mission have been in the range of $1 billion to $2.6 billion.

The draft authorization bill doesn't address the long-term spending projections or schedules for missions to the moon and Mars. Rather, it advocates a step-by-step, "go-as-we-can-afford-to-pay" approach. That carries the risk of giving NASA an ambitious goal without adequate funding to get there — which was the fatal flaw in President George W. Bush's plan to send astronauts to the moon.

The bill is likely to join the Obama administration's budget proposal as one of the starting points for debate over the future of the space effort. Yet another starting point should come to light when Senate Democrats lay out their version of the NASA authorization bill.

More about space visions:

• Which way to Mars? Moon or asteroid?
• NASA touts plan to grab asteroid
• Private spaceflight study aims for moon

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Almost a year after their deaths, NASA is paying renewed tribute this week to Sally Ride, America's first woman in space, as well as to Neil Armstrong, the first human to walk on the moon.

Ride's day in the spotlight came on Tuesday, for a simple reason: It's been 30 years since her history-making flight on June 18, 1983. Thousands thronged to the shuttle Challenger's launch, wearing T-shirts and buttons emblazoned with the slogan "Ride, Sally, Ride."

"I didn't really think about it that much at the time ... but I came to appreciate what an honor it was to be selected to be the first to get a chance to go to space," she said during an interview timed to coincide with the 25th anniversary of the flight in 2008.

If she were alive today, she'd probably appreciate the honor even more: Sunday marked 50 years since Soviet cosmonaut Valentina Tereshkova became the first woman in space. And on Monday, NASA named a new class of astronauts that included as many women as men — which is a first for the space agency. 

After her celebrated ride on the STS-7 mission, Ride went on to a successful career as a physicist and educator. She passed away in July at the age of 61, after a 17-month battle with pancreatic cancer — but the educational organization she founded, Sally Ride Science, keeps her legacy alive to this day.

To mark the 30th anniversary of Ride's launch, NASA TV is airing two tributes on Tuesday night: A look back at STS-7, titled "Sally Ride: A Ride to Remember," is being shown at 8 p.m. ET. "Sally Ride: How Her Mission Opened Doors," a program that was recorded at the Smithsonian's National Air and Space Museum, comes on at 9:30 p.m. ET.  If you miss those shows on TV, never fear: "A Ride to Remember" and the Smithsonian tribute are both on YouTube.

Slideshow: Astronaut Sally Ride

AFP/Getty Images

See images from the life and career of astronaut Sally Ride, the first American woman to fly in space.

Launch slideshow

Slideshow: Neil Armstrong: 1930-2012

See images from the career of astronaut and American hero Neil Armstrong.

Launch slideshow

Thursday is this week's big day for Neil Armstrong: The most famous of NASA's moonwalkers passed away last August at the age of 82, after suffering heart problems. He made history on July 20, 1969, when he left those first footprints on the moon's surface during the Apollo 11 mission. "That's one small step for [a] man, one giant leap for mankind," Armstrong declared.

Since his death, Armstrong has been memorialized in his native Ohio, at Florida's Kennedy Space Center and at Washington Cathedral. Thursday's ceremony is set in a different locale: Johnson Space Center in Texas, where Armstrong spent years practicing for his date with history.

Among those paying tribute will be Armstrong's Apollo 11 crewmates, Buzz Aldrin and Michael Collins; Ellen Ochoa, director of Johnson Space Center; family members and longtime associates.

The memorial service begins at 11 a.m. ET (10 a.m. CT), with a tree dedication ceremony at the center's Memorial Tree Grove following the service. Live video will be streamed via NASA TV.

The stream of honors won't end this week, for Armstrong or for Ride: President Barack Obama is awarding Ride the Presidential Medal of Freedom posthumously, in honor of her achievements in space as well as in education. Meanwhile, Congress is considering a plan to put Armstrong's name on Dryden Flight Research Center in California.

This weekend's supermoon provides a prime opportunity to pay tribute to Sally Ride and Neil Armstrong. When you look at that big full moon, just remember there's a "little corner" of the lunar surface that's named after Ride. As for Armstrong, here's what the moonwalker's family said last year: "For those who may ask what they can do to honor Neil, we have a simple request. Honor his example of service, accomplishment and modesty, and the next time you walk outside on a clear night and see the moon smiling down on you, think of Neil Armstrong and give him a wink."

More about Armstrong and Ride:

• Video: Sally Ride's launch in 1983
• Video: Remembering Neil Armstrong
• TODAY: 10 incredible female firsts
• Cosmic Log archive for Neil and Sally

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

It doesn't take an Einstein to see that international differences can still crop up on the final frontier: Take the case of the European Space Agency's Einstein cargo craft, for example. Russian concerns about some potentially moldy cargo bags caused a holdup in the schedule for unloading seven tons of supplies.

The Albert Einstein Automated Transfer Vehicle linked up with the International Space Station on Saturday, delivering a payload that included scientific experiments, clothing, spare parts and an assortment of European-style goodies such as tiramisu and lasagne.

Italian astronaut Luca Parmitano couldn't wait to get at the cargo. "There is nothing like the promise of an Italian dinner that I will offer from my personal supply to entice my colleagues to work quickly and well!" he wrote on his blog.

It took longer than expected to start the job, however. A source at ESA told NBC News that the Russians were dissatisfied with the decontamination procedures as they applied to some bags of NASA gear in the shipment. That report was confirmed in NASA's daily status report for the space station, which said that "Russian management expressed concerns with suspected microbial growth on some of the cargo bags in the vehicle."

As a result, the hatch opening was delayed for a day while NASA and the Russians worked out the logistics for wiping down the bags with fungicide. Mission managers agreed to have the crew disinfect 21 cargo bags for possible mold, and Parmitano was finally given the go-ahead to open the hatch early Tuesday.

NASA

The European Space Agency's Einstein cargo craft docks with the International Space Station on Saturday.

NASA

Mold discolors a panel where International Space Station crew members hung their exercise clothes.

Fungi and other microbes are a real gross-out in orbit: All sorts of "microbeasties," including several dozen species of bacteria and fungi, were found on Russia's Mir space station in its latter years. The International Space Station hasn't been immune from mold, either: Here's a particularly yucky picture of a panel where space station astronauts hung their exercise clothes to dry.

NBC News space analyst James Oberg, who has been following the fungus ruckus over the past couple of days, says the tiff may have had more to do with how the original decontamination procedures were documented — but in any case, the snag reinforces a bigger lesson about the space effort's safety culture.

"It's a well-established principle of spaceflight safety that, under uncertainty, you don't 'assume the best,' you make sure the worst cannot be true," Oberg said. "And if you're not sure you decontaminated these items to rigorous standards, then you do it again, to make sure."

Buon appetito, Luca!

More about the space station mission:

• Albert Einstein bringing the goods
• Trio makes it to space station in record time
• How to shave your head in space

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

NASA

An artist's conception shows a robotic probe, powered by a solar electric propulsion system, closing in to corral an asteroid. NASA is aiming to send out such a probe in 2017.

NASA's latest "Grand Challenge" is a biggie: Can you think of better ways to find potentially threatening near-Earth asteroids and do something about those threats? Your ideas could become part of the space agency's vision for the next decade.

The Asteroid Grand Challenge was announced on Tuesday at NASA Headquarters in Washington, but a lot of the details still have to be filled in. For instance, what are the specific tasks to be covered by the challenge? How much money will it take to stimulate the required innovations? Over the next month, NASA is gathering ideas under the terms of a request for information, with the aim of setting up a game plan for the years ahead.

"The purpose of the Grand Challenge is a call to action to continue the awareness around the issue of asteroid threats," Jason Kessler, NASA's program executive for the Asteroid Grand Challenge, told NBC News.

The program complements NASA's initiative to identify and bring back an asteroid so that astronauts can study it in the vicinity of the moon. It also meshes with NASA's long-running program to identify near-Earth asteroids.

"NASA already is working to find asteroids that might be a threat to our planet, and while we have found 95 percent of the large asteroids near the Earth's orbit, we need to find all those that might be a threat to Earth," NASA Deputy Administrator Lori Garver said in an agency news release. "This Grand Challenge is focused on detecting and characterizing asteroids and learning how to deal with potential threats. We will also harness public engagement, open innovation and citizen science to help solve this global problem."

All this interest in asteroids got an extra jolt in February when a meteor blast sent a shock wave sweeping over Siberia, injuring more than 1,000 people. The 55-foot-wide (17-meter-wide) space rock behind that flare-up was relatively small, as space threats go, but even somewhat larger rocks are difficult to detect in advance using current tools. The Grand Challenge is meant to stimulate the development of new tools and techniques, Kessler said.

For instance, the program might encourage the development of nanosatellites equipped with expandable pop-out mirrors that could do a better job of detecting dim asteroids. It could offer prizes for improving the software that models an asteroid's shape. Or it could establish school observation networks to bring the power of crowdsourcing to asteroid detection.

"I guarantee you there's a number of great ideas out there that I'd never come up with," Kessler said. "We're being very deliberate in not saying 'this is the way it's going to be,' except to say this is how it's going to be to promote, engage and solicit ideas from the myriad number of great thinkers."

The program is being supported with funds that are being set aside for asteroid detection, but it's too early to estimate how much money the Grand Challenge would get, Kessler said.

The Obama administration has proposed spending $47 million over the next fiscal year on the entire asteroid detection effort, with $7 million of that to be used specifically to prepare for the asteroid-grabbing mission and the Asteroid Grand Challenge. The current plan calls for a robotic probe to be sent out toward an asteroid in 2017, so that it can be brought back for study by astronauts around 2021. Although the target asteroid hasn't yet been identified, NASA has said it would be in the range of 7 to 10 meters wide. There's a chance that the probe might break off a piece of a bigger asteroid and bring it back as an alternative.

Update for 10:20 p.m. ET June 18: The B612 Foundation has been working for years to raise awareness on the asteroid threat, and is also trying to raise money for an asteroid-hunting space telescope. Former NASA astronaut Ed Lu, the foundation's CEO, issued this statement relating to NASA's Grand Challenge:

"This morning, the White House and NASA announced an Asteroid Grand Challenge, 'focused on finding all asteroid threats to human populations and knowing what to do with them.' This directly mirrors the mission of the non-profit private B612 Foundation and our Sentinel Mission, and we strongly applaud NASA and the Obama administration for their leadership in raising the visibility of this critical issue and for establishing detection of asteroids as a national priority. The administration has called for a team 'of the best and brightest' working on this together, and we look forward to increased collaboration and partnership.

"There are one million asteroids with the potential to impact Earth with energy large enough to obliterate any major city. We believe that the goal must be to find these one million asteroids — anything less, in our opinion, would not meet the intent of this Grand Challenge."

More about asteroids:

• Asteroid perils and profits draw interest
• Amateurs boost hunt for asteroids
• Cosmic Log archive on asteroids

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Laser-scanning technology reveals that the Cambodian lost city of Mahendraparvata, dating back to a time before Angkor Wat, was much more extensive than previously thought. The latest word about the high-tech hunt for hidden ruins came over the weekend in an on-the-scene report from Australia's Fairfax Media.

Archaeologists have known about the Hindu-Buddhist-influenced city, situated about 25 miles (40 kilometers) north of the better-known Angkor Wat temple complex, for decades. Some of the ruins rank among the tourist attractions on the holy Khmer mountain known as Phnom Kulen ("Mountain of the Lychees"). However, experts weren't sure how extensive the site was ... until now.

"We're talking about a city that is more than 1,000 years old and is all underground. If you didn't know, you might think it's natural," Stephane De Greefe, the archaeological project's lead cartographer, told Cambodia Daily. 

The Khmer Archaeology Lidar Consortium set up an aerial survey of the Mahendraparvata site and its surroundings, using a technique known as lidar (short for "light detection and ranging"). The process involves flying an instrument-equipped helicopter over the area, bouncing pulses of laser light off the ground below, and then analyzing the scattered light readings to produce a 3-D map of the terrain beneath the jungle's vegetation.

Billions of data points and about 5,000 digital photographs were collected during a week's worth of aerial surveys, taking in an area amounting to 143 square miles (370 square kilometers).

'Eureka moment'
University of Sydney archaeologist Damian Evans told Fairfax Media that seeing the map displayed on a computer screen marked the "eureka moment" in a years-long search. The readings revealed dozens of temple sites, hundreds of mysterious mounds that may represent burial sites, and traces of canals and roads criss-crossing the area.

An on-the-ground expedition followed, during which the team came across two temple sites that may still be intact, and a cave with centuries-old carvings that may have been a refuge for hermits during the Angkor period.

Phnom Kulen served as a center of the Angkor civilization between the ninth and the 16th centuries. Tradition has it that Mahendraparvata was where the founder of the Khmer Empire, Jayavarman II, celebrated his people's freedom from Javanese control in the year 802. Angkor Wat was built nearby more than 300 years later.

How a city got lost
Why did Mahendraparvata fade away? "We see from the imagery that the landscape was completely devoid of vegetation" at some point during the site's history, Evans told Fairfax Media's Lindsay Murdoch. "One theory we are looking at is that the severe environmental impact of deforestation and the dependence on water management led to the demise of the civilization. ... Perhaps it became too successful to the point of becoming unmanageable."

Some reports have made it sound as if Mahendraparvata was only now being discovered, but Evans told Cambodia Daily that the real point behind the research has to do with how lidar resolved the debate over the lost city's extent. Lidar surveys are becoming a routine part of "lost city" quests — including the discovery of centuries-old ruins in Honduras that may be linked to the legendary city of Ciudad Blanca, and an extensive survey of Caracol, a Maya center in Belize.

Details about the Cambodian project are to be published in the Proceedings of the National Academy of Sciences.

Update for 6:30 p.m. ET June 17: The Proceedings of the National Academy of Sciences just sent journalists a pre-publication draft of the paper submitted by Evans and his colleagues — suggesting that Mahendraparvata as well as Angkor Wat were part of a vast urban network.

"We identify an entire, previously undocumented, formally planned urban landscape into which the major temples such as Angkor Wat were integrated," the researchers write. "Beyond these newly identified urban landscapes, the lidar data reveal anthropogenic changes to the landscape on a vast scale, and lend further weight to an emerging consensus that infrastructural complexity, unsustainable modes of subsistence and climate variation were crucial factors in the decline of the classical Khmer civilization."

The researchers say their mapping reveals a pattern of regular "city blocks," within which mounds and ponds were built to create temple precincts. Such cityscapes existed in ancient Angkor as well as the Phnom Kulen region and another area farther northeast, known as Koh Ker.

"These 'urban temples' are not isolated; rather, they are nodes in an increasingly concentrated medieval cityscape," they said.

Evans et al. / PNAS

A map of northwest Cambodia provides an overview of the areas where lidar imagery was acquired, indicated with yellow shading. The background data is from NASA's Shuttle Radar Topography Mission.

Evans et al. / PNAS

Lidar imagery shows the central area of Angkor, with the "walled city" of Angkor Thom above Angkor Wat. Red lines indicate post-medieval features, including roads and canals. The other features are from the Angkor era.

The paper echoes Evans' comments about the potential environmental roots of the Khmer Empire's decline: "The archaeological record shows that episodes of failure were commonplace within the hydraulic infrastructure within the medieval period. ... For several centuries at Angkor, episodic renovation of the water management system offered a series of provisional solutions that were adequate for mitigating the risk of low rainfall on an annual scale. Eventually, however, the civilization was confronted with decadal-scale megadroughts in the 14th and 15th centuries."

The researchers speculate that those megadroughts triggered the doom of Cambodia's megacities. In that, they see a parallel to the classic Maya civilization, which is thought to have gone into decline due to a similar pattern of deforestation and drought. And they include a chilling observation about our own era, attributed to University of Sydney archaeologist Roland Fletcher: "If the infrastructure of low-density cities is inherently liable to be or to become a constraint on the viability of a city’s daily life, then this is an issue of some serious consequence for our engagement with a future of giant, low-density cities."

More about lost cities:

• Scientists share images of Honduran ruins
• Atlantis thought to be found off Spanish coast
• Lost pyramids spotted by space scientists
• Gallery: Seven tales of cities lost and found

The study to be published in the Proceedings of the National Academy of Sciences is titled "Uncovering Archaeological Landscapes at Angkor Using Lidar." In addition to Evans, Fletcher and De Greef, the authors include Christophe Pottier, Jean-Baptiste Chevance, Dominique Soutif, Boun Suy Tan, Sokrithy Im, Darith Ea, Tina Tin, Samnang Kim, Christopher Cromarty, Kasper Hanus, Pierre Baty, Robert Kuszinger, Ichita Shimoda and Glenn Boornazian.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Suza Scalora / Getty Images stock

Researchers have found ample links between a father's proximity to his children and his levels of hormones associated with nurturing.

The trick to fatherhood has a lot to do with the brain — and how close a dad gets to his kids. At least that's the message from a mounting pile of research into the neurological and hormonal cues that translate into fatherly nurturing. And what better time to keep that message in mind than on Father's Day?

"Mothers have an advantage, in that the hormones of pregnancy give them a head start and get them primed to be nurturing," said James Rilling, an anthropologist at Emory University who specializes in studying the neurological basis of social behavior. "In particular, when women give birth, there's a big surge of oxytocin, and oxytocin is also released during breastfeeding. Fathers don't have that."

Oxytocin has been called the "love hormone," even though its effect isn't always that lovely. It's thought to deepen the bond that a mom has with her newborn. But what about the dads, who don't get pregnant or breastfeed? It turns out that a father's interactions with his children produce a similar rise in oxytocin levels.

Researchers have found that emotionally involved fathers feel other hormonal effects: reduced levels of aggression-promoting testosterone; higher levels of prolactin, a lust-squelching hormone that shows up in women during breastfeeding and in men after sexual climax; and higher levels of vasopressin, a hormone linked to bonding as well as the maternal stress response.

It turns out that fathers get many of the same rushes that mothers do from parenthood — but the payoff depends on proximity and interaction. For example, researchers see the effect if the child sleeps with the parents, if the father recognizes and responds to the baby's cries, if Dad plays with the kids. When that proximity isn't present, the fatherhood effect isn't as strong.

"There seems to be some kind of fundamental social-neurobiological framework that comes into play when fathers interact with their kids," said Lee Gettler, an anthropologist at Notre Dame who worked on the prolactin study.

Why is it that the mothers and fathers come to the same hormonal response through different paths? "It may be that the most parsimonious way to engineer a paternal brain would be to take the circuitry that was already in place for maternal care, and maybe tweak that," Rilling said. "That might be the reason why there's some overlap there."

James Swain et al. / U. of Michigan

This functional magnetic resonance image shows areas of heightened brain activity when a father hears his own child's cries. Notable areas of activity include the frontal cortex, insula putamen, thalamus and superior temporal cortex.

Or it may merely be that when it comes to parenting, familiarity breeds fatherhood. University of Michigan psychiatrist James Swain has been analyzing a huge data set of MRI snapshots to see how maternal and paternal brains respond to the cries of their own babies and the children of strangers. He and his colleagues have found that brain activity patterns don't change as quickly for fathers as they do for mothers.

"I joke that this may be the physiological basis for why a father can roll over in bed when the baby's crying at 3 weeks," Swain told NBC News.

However, by the 4-month mark, "the fathers seem to catch up," Swain said. And there's some indication that the brain patterns for stay-at-home dads are more similar to the changes that moms go through. Swain and his colleagues are still trying to figure out exactly how the parenthood effect works on the neurological level — and how moms and dads get to the same place by different hormonal paths.

Rilling said the study of the fatherhood effect is a "wide open frontier."

"Humans are an alloparental species, which means mothers get help," he said. "In some cultures it's the father, but in other cultures it's the grandmother, the aunts, the older children. Fathers seem to be particularly important in modern developed Western nations like the U.S., because there are so many people who are living in isolated nuclear families, largely separated from their extended family. That limits the number of potential helpers out there. ... It's really important that fathers step up."

More about science and fatherhood:

• How fatherhood made us human
• Mice get less violent when they're dads
• Scientists see why fathers matter

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Asteroid 1998 QE2 turns while its moon zips upward. Credit: Ellen Howell / NASA / Arecibo

The Arecibo Observatory in Puerto Rico has captured the most detailed radar images yet of asteroid 1998 QE2 and its newly discovered moon.

A sequence of pictures released on Friday shows the 1.9-mile-wide (3-kilometer-wide) asteroid rotating in outer space while its 2,500-foot-long (750-meter-long companion zips around it. The asteroid and its moon sped past Earth harmlessly at a minimum distance of 3.6 million miles (5.8 million kilometers) on May 31.

"Asteroid QE2 has no chance of hitting Earth," Michael Nolan, head of the 1,000-foot-wide (300-meter-wide) telescope's asteroid radar group, said in a statement from the Universities Space Research Association, or USRA.

The Arecibo Observatory, sponsored by the National Science Foundation, is the world's largest and most sensitive single-dish radio telescope. Astronomers have been using Arecibo and NASA's Goldstone radar installation in California to track the movements of 1998 QE2 and its moon after its close encounter. Radar readings have revealed craters on the surface of the large rock.

Scientists estimate that one-sixth of all near-Earth asteroids have moons. "QE2's moon is roughly one-quarter the size of the main asteroid," said Patrick Taylor a USRA research astronomer at Arecibo. "Similarly, our moon is also approximately one-fourth the size of our planet."

Analyzing the motion of QE2's moon will help scientists determine the mass of the main asteroid.

"Being able to determine its mass from the moon helps us understand better the asteroid's material," said Ellen Howell, a USRA research astronomer who captured radar images of the asteroid at Arecibo and optical and infrared images using the Infrared Telescope Facility in Hawaii. The optical images can provide spectral data, revealing what the asteroid is made of.

"What makes this asteroid so interesting, aside from being an excellent target for radar imaging, is the color and small moon," Howell said in the USRA statement. "Asteroid QE2 is dark, red, and primitive — that is, it hasn't been heated or melted as much as other asteroids. QE2 is nothing like any asteroid we've visited with a spacecraft, or plan to, or that we have meteorites from. It's an entirely new beast in the menagerie of asteroids near Earth."

1998 QE2 gets its name from the timing of its discovery. The "QE2" refers to the order in which the asteroid was found during the latter half of August 1998. For what it's worth, 1998 QE2's diameter is nine times the length of the ocean liner Queen Elizabeth 2.

More about asteroids:

• Huge asteroid's flyby captured in new video
• 1998 QE2 sails past earth, leaving lessons behind
• Cosmic Log archive on asteroids

USRA's Michael Nolan led the radar observations of QE2, along with Ellen Howell, Patrick Taylor, Alessondra Springmann, Sean Marshall of Cornell University, and Mariah Law of Embry-Riddle Aeronautical University, in collaboration with the Near-Earth Object radar team at NASA's Jet Propulsion Laboratory and Goldstone Observatory in California. Observations continued through Thursday morning.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

NASA file

A photo from the Apollo 17 mission to the moon in 1972 shows a makeshift fender on the crew's lunar rover, constructed from laminated maps and duct tape. "Just call me the little old fender maker," mission commander Gene Cernan said.

Over the past half a century, duct tape has been keeping NASA's astronauts alive, putting airplanes back together, making race cars speedier and patching up millions of fix-it projects. It's even been used to remove warts. But the makers of duct tape aren't resting on their sticky, gray laurels: On the contrary, engineers and designers are adding some new twists to the decades-old standby.

"Ten years ago, I used to hear kids say, 'Oh, my dad uses that to fix everything,'" Scott Sommers, director of marketing for ShurTech Brands, told NBC News. "Now I hear the dads say, 'Oh, my kids make everything out of that stuff.'"

ShurTech makes one of the best-known brands of duct tape, known as Duck Tape, and is the motive force behind this weekend's Duct Tape Festival in Avon, Ohio, the company's corporate headquarters. The annual event is scheduled to coincide with Father's Day — which is apt, considering how many dads have gotten out of a tough fix thanks to those silvery rolls of adhesive.

"I hope that women never find out about duct tape," humorist Dave Barry joked, "because once they do, men will no longer serve any useful purpose."

NBC News Travel: Thousands rock the roll at Duct Tape Festival

Duct tape's triumphs add up to a list that would make TV's MacGyver envious:

• The plastic-coated tape first came into its widespread use during World War II, when the U.S. military used it as a waterproof sealant. During the Vietnam War, it was used to patch up helicopter rotor blades — earning it the nickname "100-mph tape."
• When the Apollo 13 spacecraft suffered a crippling explosion in 1970, ground controllers came up with a plan to have the crew build improvised air filters using duct tape. Without that fix, "the crew would not survive," one of the Apollo engineers said. Two years later, Apollo 17 commander Gene Cernan used what he called "good old-fashioned American gray tape" to fix a fender on the lunar rover.
• When an Alaska bush pilot discovered that a brown bear had ripped his plane virtually to shreds, he had to call on friends to help put it back together with sheets of plastic wrap and a case of duct tape. A few days of work made the plane airworthy enough to fly back to civilization. "I think that's as close as you can get to MacGyver without going to outer space," said Jeff Malmer, a member of the research and development team for 3M, which makes Scotch-brand duct tape.
• NASCAR race crews routinely use duct tape to hold things together or modify airflow for peak performance — earning it the upgraded nickname "200-mph tape." It's especially cool if the crew uses color-coordinated tape.
• Some experts have touted duct tape as a wart-removal therapy. Supposedly, the adhesive tape works by irritating the skin and stimulating the body's immune system to attack the virus that causes the warts. Or maybe it just covers up the skin in such a way that makes it less hospitable to the virus. Does it really work? ShurTech's Sommers shies away from the question: "For legal reasons, I can't say we promote it," he said. 

Today, duct-tape manufacturers are reluctant to mess too much with success. "The majority of people who buy duct tape buy it to have around, just in case, and therefore we remain focused on making as much of a universally focused product as possible," Sommers said. But ShurTech is introducing some manufacturing innovations, such as a technique called "co-extrusion" that casts the plastic film at the same time that the rest of the tape (cloth mesh and rubber-based adhesive) is made.

The basic formula occasionally gets tweaked to respond to the marketplace: ShurTech offers different grades of tape for different applications. 3M has its own heavy-duty tape, called "Scotch Tough," as well as transparent duct tape and a type of tape that doesn't leave a rubbery residue when you rip it off.

And then there are the colors and patterns: Both companies have capitalized on duct tape's growing popularity as a craft item. "The kids have started to make fun things, and fashion things," Sommers said. 3M's marketing manager for Scotch duct tape, Laura Maciejewski, told NBC News that "it's really the girls who are using it." ShurTech offers Duck Tape designs with college themes, while 3M has marketing deals for Barbie, Batman and Superman tape.

Is there anything duct tape can't do? Well ... yes.

"What's ironic about duct tape is that it's really not the best product for sealing duct work," Malmer said.

More about sticky science:

• Look out, Spider-Man! Gecko inspires new glue
• The science of stickiness revealed
• Bacteria make world's strongest glue

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

No one expects the Superman saga to serve as a scientific treatise — but the back story for "Man of Steel," the latest reboot of the 75-year-old tale, does play off some of the latest discoveries on the final frontier. And the saga could provide a leaping-off point for future technological advances as well.

Just ask James Kakalios, who literally wrote the book on pulp-comic science, titled "The Physics of Superheroes." Superman's dazzling array of superpowers — ranging from super-strength to X-ray vision and freeze-breath — may be beyond the edge of plausibility, but Kakalios argues that merely musing over how they might work fires the imagination for more down-to-Earth inquiries.

"It's a parlor game reflecting what we do in research anyway — 'what if,' and 'what do I need to have happen for this to exist.' If you do it with superheroes, or if you do it in the real world, it's the same mental muscles that are being exercised," he told NBC News.

Kakalios noted that the first incarnation of Superman, in 1938's Action Comics No. 1, was inspired by Edgar Rice Burroughs' stories of "John Carter on Mars," in which an earthly adventurer took advantage of Mars' lower gravity to leap around and perform feats of seeming super strength. Comic-book writer Jerry Siegel turned that around by imagining that Superman came from a supermassive alien planet called Krypton. "We're the planet that has the weak power," Kakalios said.

So far, so good — but that's not the whole explanation for Superman's powers. The official story is that Superman's body was originally acclimated to Krypton's red sun, and is now able to soak up lots more power from our yellow sun. That gets into shakier ground. "Once you make that argument — that if the dominant wavelength shifts by 80 nanometers, that's enough to enable someone to bend steel in their bare hands and have super-breath — then you've entered the realm of fantasy," Kakalios said.

When it comes to planetology, however, Siegel and "Superman" artist Joe Shuster were ahead of their time: It's only recently that astronomers have come to the conclusion that lots of red dwarf stars may have planets, and that those planets may be as close as 13 light-years. What's more, planet hunters have proposed that super-Earths — that is, terrestrial planets more massive than our own — may well be superior when it comes to fostering life.

At the behest of DC Comics, astronomer Neil DeGrasse Tyson even pinpointed a red dwarf that could serve as a real-life stand-in for Krypton's red sun: LHS 2520, 27 light-years away in the southern constellation Corvus. It's not known whether LHS 2520 has any planets at all, let alone a Krypton-like super-Earth. But at least DC recognizes that exoplanets are no longer the stuff of pulp fiction.

Slideshow: Men of Steel

Getty Images

From comics to movies, the many incarnations of Superman.

Launch slideshow

Here are a few more examples showing how superpower musings spark real-life science:

Super-suits: The Man of Steel supposedly has a body that's impervious to almost everything except Kryptonite, which led researchers at the University of Leicester to calculate what kind of muscles or skin Superman would need to stop a bullet. Surprise, surprise: The physics don't work out. Even if you could leap tall buildings, your muscles still wouldn't be dense enough to be bulletproof. And in order for skin to stop a bullet, the required density would be "unreasonably high, even by assumed extraterrestrial standards," the researchers reported. Kakalios said it'd be more plausible for Superman to rely on a super-suit woven from graphene, a real-life super-strong substance. "You wouldn't need to be bulletproof if you had something like that," he said.

Fortress of Solitude: In previous movies, Superman's Fortress of Solitude was grown from a crystal — but based on the trailers, the filmmakers behind "Man of Steel" are going for a more organic look this time around, which Kakalios likes. "It almost looks like something from the 'Prometheus' or 'Alien' films," he said. It's more plausible to imagine an organic, nanoscale, self-assembling process that could produce large carbon-based structures — or that graphene super-suit.

Manipulating mass: In a paper titled "A Unified Theory of Superman's Powers," theoretical physicist Ben Tippett proposed that all of Superman's abilities could be explained if you just supposed he had the ability to manipulate inertial mass on scales ranging up from atoms to speeding locomotives and tall buildings. Inertial manipulation is often cited in science fiction as a way to get from place to place at faster-than-light speeds — so that would explain Superman's trip from Krypton to Earth as well. Researchers have been thinking about ways to do this in real life for more than a decade. So far, they're nowhere close to a breakthrough, but who knows? If the Large Hadron Collider's studies of the Higgs boson lead to a deeper understanding of the nature of particle mass, inertial manipulation could become a reality. Or at least become more plausible.

Do you have any musings on the real-life science inspired by the Superman saga? Feel free to weigh in with your comments below.

More about the Man of Steel:

• Super Square must adjust to an 'Iron Man' world
• Rating Hollywood's hunky heroes
• The science of Superman, circa 2006

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

A Chinese spaceship made a successful automated docking with an orbiting module on Thursday, marking one more small step toward full-fledged space station operations.

The Shenzhou 10 spacecraft completed the procedure for docking with the Tiangong 1 module at 1:18 p.m. Beijing time (1:18 a.m. ET),  delivering China's three latest spacefliers to their temporary home, the Xinhua news agency reported.

This was the first docking maneuver of the Shenzhou 10 mission — which was launched Tuesday, representing China's fifth crewed spaceflight since 2003. Tiangong (which means "Heavenly Palace" in Chinese) has been circling the planet for almost two years as a test platform for docking and orbital operations. In 2011, two unmanned, automated dockings were conducted, and the crew of Shenzhou 9 made two test dockings last year.

Three hours after docking, Shenzhou 10's three crew members — including Nie Haisheng, Zhang Xiaoguang and China's second woman astronaut, Wang Yaping — opened the hatch and floated inside the module.

During the current 15-day mission, Shenzhou 10's crew is due to conduct scientific and technical experiments aboard Tiangong 1 and deliver a lecture to students back on Earth. The spacefliers are also scheduled to unhook from the module and come in again for a manual docking.

Tiangong 1 will remain in service for only another three months, Xinhua said. China plans to deorbit the module later this year, and then send up more advanced labs for further testing. Beijing's space strategy calls for the creation of a full-fledged space station by 2020. China is not a participant in the 15-nation International Space Station project, in part because of U.S. opposition.

CCTV / AFP - Getty Images

This still photo taken from China Central Television shows Chinese astronaut Nie Haisheng entering the Tiangong 1 space module on Thursday.

More about China in space:

• Chinese space program continues to improve
• Chinese trio launched for orbital tests

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.