NASA / STScI

Mars looms large in a Hubble Space Telescope photo - and in the imaginations of those who have signed up for a one-way trip to the Red Planet. "It's not that I'm trying to get away," says 18-year-old Kayli McArthur, one of tens of thousands of applicants. "It's like I'm trying to strive for something more."

A one-way trip to Mars sounds like something you'd wish on your worst enemy — so why would more than 78,000 people from around the world pay up to $75 for a chance to die on another planet?

"I can say I have an ulterior motive," said David Brin, who has written more than a dozen science-fiction novels — including "The Postman," which was turned into a Kevin Costner movie in 1997. "I'd get a lot of writing done, and it might be memorable."

As a master of hard science fiction, the 62-year-old Brin knows better than most applicants what the first Red Planet settlers would face if they're sent off in 2022, as the Dutch-based Mars One venture has proposed.

The settlers would have to be sealed up in habitats, protected from harsh radiation, supplied with machine-made air and water, and nourished by whatever food can be grown on a cold, barren planet. They'd have to keep their sanity, millions of miles away from their families and Mission Control. Worst of all, they'd have to face the fact that there's no guarantee of ever going back.

Will this scheme actually work? "I give it a low probability of happening," Brin said, "and I don't consider it to be the most responsible thing I've ever seen."

Nevertheless, the venture has an attraction for Brin and tens of thousands of others, The ages of those listed in Mars One's database range from 18 to 71. All those applicants are facing a long road even before the first four-person crew gets off the planet. Mars One is accepting applicants through Aug. 31. The field of applicants would first be whittled down by panels of experts. Then they'd undergo trial by reality TV, followed by years of training.

"This may sound crazy, but it kind of reminds me of 'The Hunger Games,'" said Kayli McArthur, an 18-year-old student who's one of the youngest Mars One applicants. "It's cool that it would be televised, but that's not my whole thing."

On the other end of the age spectrum, 71-year-old psychiatrist Sanford Pomerantz is a little surprised that it's taking this long to get something like Mars One off the ground. "I thought by now we would have colonized Mars," said Pomerantz, who's currently the oldest applicant on Mars One's list.

So what's the appeal of Mars One? It's too early for Brin, McArthur and Pomerantz to give a lot of thought to their adventure on Mars, let alone their death on Mars. Instead, they're focusing on the adventure here on Earth. Here's what's behind their thinking:

Mars One

Click on the image to go to David Brin's Mars One application video.

David Brin: 'My main purpose is the conversation'
Brin sees Mars One as just one of a number of ventures aimed at expanding humanity's frontier, ranging from Virgin Galactic's suborbital space tours to Golden Spike's moon missions. "It's emblematic of the new era that we're about to enter at long last — what I call the barnstorming era," he said.

Like the daring airplane fliers of the 1920s, these 21st-century space barnstormers are willing to take bigger risks in hopes of providing bigger thrills — and eventually, earning bigger payoffs. The Mars One project is "a great way to get the discussion going," Brin said.

"You have to assume that it may not work, and that there will be a statue of you on Mars someday," he said. "I'm aware of the tradeoffs, and I'm willing to explore it further, but largely my main purpose is the conversation. We've got to be talking about how we can be a more exploratory people — a more interesting people, if you like."

Brin doesn't doubt that Mars One will find plenty of qualified (and interesting) people willing to take the risk.

"People who cannot imagine any sane person making that choice simply aren't envisioning the wide range of human diversity," said Brin, who has three children in school. "Consider what I told my family. By the very earliest date that Mars One might launch, I expect to be a spry 75-year-old whose kids are already successfully launched, and who might spend a few years doing something truly remarkable."

Even if it means dying on alien soil? Brin isn't completely sure he'd go that far, but he's willing to bet that others would.

"I think you'll find tens of thousands of people who, under those circumstances, will at least ponder it seriously," Brin said.

Mars One

Click on the image to go to Kayli McArthur's Mars One application video.

Kayli McArthur: 'I'm trying to strive for something more'
McArthur, a freshman at the University of Arizona, is one of more than three dozen 18-year-olds on Mars One's list of applicants. Ever since she applied, she's been hearing that she has her whole life ahead of her, so why would she want to leave it all behind for Mars?

"Being young doesn't make me want to do it any less because I have my whole life ahead of me," she said. "It makes it more exciting. ... I love all my friends, my guy friends, my family. It's not that I'm trying to get away. It's like I'm trying to strive for something more."

She has long dreamed of going into outer space, and she figures that her future degree in materials science would come in handy for creating the first interplanetary settlement. "Going to Mars, there are so many opportunities for that," she said. 

So far, her family hasn't stood in her way. "My family jokes, like, 'Oh, Kayli, have your fun with it,'" she said. If the selection process gets more serious, she suspects she might face more resistance from her parents. But not from her grandfather.

"My grandpa is a retired three-star [general] in the Air Force," she said. "We were talking about it. I get really worked up and excited, and he was talking about it, too, and being realistic about it. He said, 'That would be so cool if you were able to do it.' ... I know my grandpa would totally support me."

Mars One

Click on the image to go to Sanford Pomerantz's Mars One application video.

Sanford Pomerantz: 'Grandpa is going to Mars!'
Pomerantz is old enough to remember when the idea of sending people into outer space seemed as far out as the idea of sending people on a one-way trip to Mars seems now. One of the books that made an impression on him in grade school was Robert Heinlein's "Red Planet: A Colonial Boy on Mars," which was published in 1949.

"I started as a physics major in the university, but then I got accepted into med school and changed directions," he said. At the age of 71, he's still a practicing psychiatrist in Topeka, Kan. But he's also still holding onto that boyhood dream of spaceflight.

"The Mars thing is exciting, because I hope it'll stimulate people to get interested in space. ... And I hope it has the secondary effect of stimulating science education, especially in the U.S.," he said.

Just as McArthur believes that Mars will need a materials scientist, Pomerantz believes the crew will need a psychiatrist. "Psychologically, it's going to be an interesting challenge, but human beings are very adaptable," he said. "It'll be exciting to go to a whole new world. It'll be a major step in human evolution."

If Pomerantz ends up being selected for the first Mars crew, he's likely to become not only the oldest human to head for the Red Planet, but the oldest human to go on any space mission. (The current record-holder is John Glenn, who flew on the shuttle Discovery when he was 77 years old.) For now at least, that prospect doesn't faze Pomerantz's three children and two grandchildren. "The grandchildren are excited," he said. "It's like, 'Grandpa is going to Mars!'"

Pomerantz became a certified scuba diver just two years ago, and he still expects to be in good physical and mental shape for liftoff in 2022. "Remember, age is a state of mind," he said. "Chronologlcally, I may be 71. ... But psychologically and physically, I'm definitely in my 20s. I look in the mirror and say, 'Who's that old guy?'"

More about missions to Mars:

• Inspiration Mars: So crazy it just might work
• Buzz Aldrin envisions US leading way to Mars
• Cosmic Log archive on Mars

David Brin's latest science-fiction novel is "Existence," which is set in the latter part of the 21st century and involves matters way beyond 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.

Canadian astronaut Chris Hadfield finished out his five-month flurry of songs, snapshots and social media from outer space with a real doozy: a rendition of David Bowie’s “Space Oddity” that even Bowie is retweeting.

The music video was months in the making: With Bowie's approval, the song's lyrics were tweaked to reflect Hadfield's return from the International Space Station on Monday aboard a Russian Soyuz craft. "Lock your Soyuz hatch and put your helmet on," Hadfield sings in the video. After showing scenes of Hadfield strumming on his guitar and gazing soulfully out the station's windows, the video winds up with a Soyuz parachuting down to its landing.

Since "Space Oddity" went up on Sunday, it's been viewed on YouTube more than 2.7 million times.

The YouTube hit caps off an orbital tour of duty during which Hadfield sent down thousands of pictures via his Twitter account, performed the first original song recorded on the space station, mixed it up with "Star Trek" icon William Shatner and unveiled Canada's new $5 bill. For the past two months, he was doing all this while serving as the station's first Canadian commander.

"He's brought space back, not just for Canadians but for the world," fellow Canadian astronaut Jeremy Hansen told NBC News.

Dreams of space
Hadfield, 53, began his path to stardom during his childhood on a corn farm in southern Ontario. Watching Neil Armstrong's first steps on the moon in 1969 inspired him to dream of becoming an astronaut when he was 9 years old. He started flying airplanes in his teens, and went on to become a fighter pilot in the Canadian Armed Forces. He's been an astronaut since 1992, and he flew on space shuttle missions in 1995 and 2001.

Last December, he finally got his shot at a long-term stint in space — and he definitely made the most of the experience.

Slideshow: The antics and artistry of astronaut Chris Hadfield

Canadian spaceflier Chris Hadfield has posted incredible pictures of the world from space. He has also explained how to brush your teeth, shave and clip your nails while weightless.

Launch slideshow

Hadfield's 28-year-old son, Evan, told NBC News that his father put in several hours a day snapping pictures and sending tweets, in addition to his usual 10-hour work shift aboard the station. "When he wasn't working directly for space station maintenance, or on one of his science experiments, he was doing something with his time to benefit people down here," Evan Hadfield said.

Evan worked long hours, too, without pay. Over the past five months, he has been managing his father's social-media accounts and taking the lead in getting videos like "Space Oddity" produced. "I work about 16 hours a day, seven days a week," he said. "Last week I worked 19 hours a day. ... I read about 13,000 to 17,000 messages a day, and that's just in the morning."

"Space Oddity" was a special case, in part due to a tangle of international copyright issues. The Hadfields started working with Bowie and his team, as well as NASA and the Canadian Space Agency, even before the astronaut's launch in December. "It was definitely something we wanted to do," Evan said.

Why do it? Chris Hadfield hinted at the reasons in a different farewell-to-space video: "Who'd have thought that five months away from the planet would make you feel closer to people?" he asked. "Not closer because I miss them — just closer because seeing this [experience] this way and being able to share it through all the media that we've used has allowed me to get a direct reflection back immediately from so many people. ... It makes me feel like I'm actually with people more, that we're having a conversation. That this experience is not individual, but it's shared and it's worldwide."

Hansen said all of Hadfield's pictures, videos and tweets could be boiled down to a simple message: "We do live on a spaceship, a spaceship called Earth, and we need to work together to protect it."

The next chapter
So what's next? After Hadfield and his two Soyuz crewmates touch down in Kazakhstan, they'll be whisked away in separate directions: Russian cosmonaut Roman Romanenko will head toward Moscow, while Hadfield and NASA astronaut Tom Marshburn will be flown directly back to NASA's Johnson Space Center in Houston for medical checks, debriefings, rest and recuperation.

"We have a lot in store for these guys over a number of weeks," Hansen said. And that's not counting a single tweet.

It's hard to believe that Hadfield will be out of the social-media spotlight for long. "We've still got a lot of stuff," Evan Hadfield said. There are still lots of photos and videos from his father's spaceflight that have yet to be shared. But not even the Hadfields know how all those visions from outer space will come out, and on what timetable.

"I don't know, and I don't even want to speculate, because what if I'm wrong?" Evan said. "I hope, I really hope that people take Dad's message to heart and continue it past his return."

Update for 12:25 p.m. ET May 14: The "Space Oddity" video viewership is up to nearly the 7 million mark, and Hadfield commented on the YouTube phenomenon shortly after his landing in Kazakhstan. "I'm very happy that ... 7 million are interested. It is very interesting and historic to be in space," Reuters quoted Hadfield as saying.

"It's part of humanity to be in space," Hadfield said in Russian. "What we were feeling, what we were doing there, the music we played, this is a big part of our lives." 

More about Chris Hadfield:

• Astronaut's artistry hits warp speed
• How Canada's top astronaut sees the world
• Cosmic Log archive on Chris Hadfield

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other 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.

This story was originally published on Mon May 13, 2013 7:49 PM EDT

Slideshow: Art of Science 2013

Mingzhai Sun and Joshua Shaevitz / Princeton

Click through the top images from Princeton University's Art of Science Competition, which features images of artistic merit created during the course of scientific research.

Launch slideshow

Worms are a source of wonder in this year's crop of aesthetically pleasing scientific images, served up by Princeton University's Art of Science Competition.

"C. instagram," one of the contest's top photos, features a wriggling network of C. elegans worms on an agar plate covered with E. coli bacteria. Ewwww, right? But when Princeton molecular biology student Meredith Wright looked at the scene through a microscope, she had a different reaction: Cooool!

"I found the pattern on this plate particularly lovely, and was able to capture it with my cell phone by holding the lens of my phone's camera up to the microscope eyepiece," she wrote. "I've since shared the photo on social networking sites and have had friends who've never been interested in biology ask me more about my work because of this photo."

Researchers don't do what they do to create beautiful pictures, but beauty often arises amid the search for scientific truth. That's what the Art of Science program is going for: Images produced in the course of scientific research that have aesthetic merit as well.

This year's theme was "Connections." Andrew Zwicker, director of science education at the Princeton Plasma Physics Laboratory, said that some of history's most exciting scientific discoveries have come from making connections between different disciplines.

"For example, with physics and biology, everyday there is a new finding showing that the two are connected in the most fascinating and profound way," he said in this year's contest announcement. "In a similar vein, connecting the aesthetics of laboratory images to their scientific importance has transformed how we look at our data and results. With the 2013 Art of Science competition, we are celebrating all manner of connections."

Meredith Wright / Princeton Art of Science Competition

"C. instagram" shows masses of C. elegans worms on an agar plate. The picture was taken with a smartphone camera through a microscope, and shared via Instagram.

The connections between beauty and truth are reflected in this year's three top-rated images. First prize goes to Martin Jucker's visualization of Earth's wind patterns in shades of red and blue. Michael Kosk's photomicrograph of crushed birch wood took second place. And third prize went to a many-branching visualization of online connections for the websites set up by the plasma physics lab and by the Lewis Center for the arts.

"These two embroidery-like figures visually give us an idea of the similarities and differences of a website devoted to science and one devoted to the arts," said the prize-winning webmasters, Paul Csogi and Chris Cane.

The three prize-winners will share $500, divided into shares of $250, $154.51 and $95.49 in accordance with the aesthetically pleasing golden ratio. Another 40 images are included in Princeton's Art of Science 2013 exhibit, which opened on Friday in the atrium of Princeton's Friend Center. The works were chosen from 170 images submitted from 24 different departments across campus.

Click through our slideshow featuring some of the pictures in the exhibit, and then be sure to visit the Art of Science website and the Art of Science Facebook page for much, much more. And don't forget to share. That's precisely what Meredith Wright hopes you'll do with "C. instagram."

"This image represents the simple pleasure of finding something beautiful when you don't expect to," she wrote, "and it shows how easy it is to connect science with new audiences by simply clicking 'share.'"

More artistic science to share:

• Solid science turns into crowd-pleasing art
• Creepy critters and cool close-ups
• How beauty was found in a slimeball

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.

Satellite imagery can serve as a time machine, revealing dramatic change in just a few seconds — but can you imagine documenting almost three decades' worth of all that change, across most of our planet's land mass? A team of imaging experts, computer scientists and journalists did. Now they've unveiled the result: a global database of zoomable, animated satellite views known as Timelapse.

"We believe this is the most comprehensive picture of our changing planet ever made available to the public," Rebecca Moore, engineering manager for Google Earth Engine and Earth outreach, said Thursday in Google's blog announcement of the Timelapse project.

Moore said the project began in 2009, when Google started working with the U.S. Geological Society to make its archive of Landsat imagery available online. The team sifted through more than 2 million satellite images, adding up to 909 terabytes of data, and selected cloudless, high-quality views for every year since 1984.

Carnegie Mellon University's CREATE Lab smoothed the views into seamless animations, and Time magazine built it all into a presentation that supplements the time-lapse animations with commentaries on climate change, urban growth and the other trends that are transforming the planet.

"I've been chiseling away at this project over the last 11 months, and am in awe of the folks who helped this come together in ways I could never have conceived on my own. Some very bright minds figured out how to make the biggest video frames ever constructed, equivalent to 900,000 HD TVs next to one another," Jonathan Woods, the Time project's executive producer (and a former colleague at msnbc.com), said in an email.

Google Earth is also hosting the Timelapse zoomable map. "Much like the iconic image of Earth from the Apollo 17 mission — which had a profound effect on many of us — this time-lapse map is not only fascinating to explore, but we also hope it can inform the global community's thinking about how we live on our planet and the policies that will guide us in the future," Moore said.

When it comes to telling the story of our changing planet, one time-lapse animation is worth a thousand words. But there's more to tell. Find out more about the trends illustrated in the seven animated images you see here:

Columbia Glacier: Alaska's retreating ice reveals how climate change is changing Earth's surface.

Dubai coastal expansion: New islands are sprouting along Dubai's coastline as part of a $14 billion land reclamation effort, arguably the largest project of its kind.

Irrigation in Saudi Arabia: Agriculture amid the deserts of Arabia? It's a growing concern, thanks to huge irrigation projects that take advantage of underground rivers and lakes. The water won't last, though: Hydrologists estimate that it'll be economical to pump water for only about 50 years. 

Lake Urmia drying up: Iran's great salt lake is not as great as it was, and the reason for that is in dispute. The Iranian government blames climate change and drought, while critics blame the dams that have been built around the lake.

Brazilian Amazon deforestation: Satellite imagery documents the loss of Amazonian forest land in Brazil due to road-building, logging and agricultural clearing.

Las Vegas urban growth: What sprawls in Vegas doesn't stay in Vegas. Landsat pictures reveal how urban development has spread out around Nevada's biggest city over the decades.

Wyoming coal mining: The Black Thunder mine in Wyoming's Powder River Basin ranks as the largest single coal mining complex in the world, according to Arch Coal, its operator. Satellite imagery shows how the mine has spread out over the decades.

More time-lapse videos:

• One World Trade Center rises
• Shuttle Endeavour traverses L.A.
• Time-lapse gallery from Photoblog

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 third of America's honeybee colonies bit the dust last winter, according to a bellwether survey of bee health. But the deaths didn't fit the typical pattern for colony collapse disorder, the mysterious malady that wipes out bunches of bees all at once. Instead, researchers suggest that last summer's drought and other common-sense factors were to blame.

The annual survey of beekeepers, conducted by the Bee Informed Partnership and the Apiary Inspectors of America, found that 31.1 percent of the colonies were lost over the winter of 2012-2013. That compares with a loss of 22 percent during the previous winter, which was exceptionally mild. It's also slightly higher than the six-year average of 30.5 percent in colony losses.

The past winter's bee death rate was roughly as high as it was during the winter of 2006-2007 — when colony collapse disorder, or CCD, was at its peak. But this time, most colonies "dwindled away rather than suffering from the sudden onset of CCD," Jeff Pettis, a U.S. Department of Agriculture bee expert who worked on the survey, said in a news release announcing the results.

University of Maryland entomologist Dennis vanEnglesdorp, who directs the Bee Informed Partnership, listed several likely causes for last winter's spike. One prime reason is the drought that swept over the Midwest last year. "When there's a drought, the bees are in poor shape with the food," California beekeeper Randy Oliver told NBC News in March.

Honeybees may have had to rely on irrigated crops rather than wildflowers for their nectar, which could have increased their exposure to pesticides, vanEnglesdorp said. He said last year's rising corn prices led farmers to replace prairie and shrubs with cornfields, further limiting the bees' foraging areas. And for part of the year, beekeepers lacked an effective treatment for Varroa mites, a type of bee parasite that was cited last week as the biggest factor behind the nation's bee die-off.

VanEnglesdorp said all these factors left bee colonies in a weakened state for the tough winter of 2012-2013. He said the beekeepers who took their hives to California in February to pollinate almond trees suffered especially high losses. Nearly 20 percent of those beekeepers said they lost 50 percent or more of their colonies over the winter.

Pettis noted that the survey stopped tracking losses at the end of April. As a result, "the 31 percent figure likely underrepresents the losses, as we saw many weak colonies that were not actually dead," he said.

Beekeepers rebuild their colonies in the spring, so a 31.1 percent loss rate isn't quite as catastrophic as it sounds. Nevertheless, vanEngelsdorp said high winter losses are changing the way commercial beekeeping is done. "All the money you're going to make in honey goes to replacing dead colonies and keeping your colonies alive," he said. "Any money you make [as profit] will be from pollination."

More about the bees:

• Die-off blamed on combination of causes
• EPA steps up pesticide review
• NBC News archive on the bee crisis

The winter colony loss survey was funded by USDA. The 6,287 U.S. beekeepers who responded to the survey managed nearly 600,000 bee colonies at the start of the survey period, or about 23 percent of the country's estimated 2.6 million colonies. A complete analysis of the survey data will be published later this year.

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 / Ken Kremer / Marco Di Lorenzo

A mosaic of images captured by NASA's Mars Curiosity rover on Sol 262 of its mission on Mars (May 2) shows its robotic arm in the foreground and Mount Sharp in the background. Two drill holes can be seen on the surface of the bedrock visible below the robotic arm's turret.

NASA's Curiosity rover is back at work in Yellowknife Bay, a rocky area inside Mars' Gale Crater — and if it takes good care of itself, it just might still be at work when humans hit the Red Planet.

At least that's the sentiment voiced by Michael Meyer, lead scientist for NASA's Mars Exploration Program, during this week's Humans to Mars Summit in Washington. "I anticipate the first astronaut we send can go and shake Curiosity's hand," he told Monday's audience at George Washington University. If that astronaut is able to come within hand-shaking distance, the gesture would serve as a thank-you for years of service by the nuclear-powered robot, Meyer said.

Last week, Curiosity resumed contact with controllers back at NASA's Jet Propulsion Laboratory after a weeks-long gap that was scheduled due to solar interference — and JPL has just finished upgrading the rover's software.

Images sent back on May 2 show the rover's robotic arm and its instrument-laden turret poised over Yellowknife Bay's bedrock. Scientist-writer Ken Kremer and his Italian colleague, Marco Di Lorenzo, assembled 13 images ("a Martian baker's dozen") into the sepia-toned panorama you see above.

"She's back and flexing!" Kremer wrote in an email. 

Within a week or so, the rover will be drilling into Martian bedrock to flesh out its scientific findings about the habitability of ancient Mars. Then it'll start heading toward Mount Sharp (a.k.a. Aeolis Mons), a 3-mile-high (5-kilometer-high) mountain in Gale Crater. Scientists are hoping that the layers of rock on that mountainside have recorded billions of years' worth of geological changes.

Because Curiosity is powered by a plutonium-fueled radioisotope thermoelectric generator, the rover could keep going for decades — assuming that there aren't any mechanical breakdowns, of course. That's what fuels Meyer's hope that there'll be a human-machine handshake someday.

More than 70 percent of Americans are confident that humans will go to Mars by 2033, according to a survey conducted in February by Phillips & Company for the Boeing Co. and Explore Mars, the nonprofit group sponsoring this week's summit. But one of the summit's headliners, NASA Administrator Charlie Bolden, said that sending astronauts to Mars can't be done without technological innovation and financial support.

"I don’t know about you, but I’m not ready," The Washington Post quoted Bolden as saying. "I don’t have the capability to do it. NASA doesn’t have the capability to do that right now. But we’re on a path to be able to do it in the 2030s."

Will humans ever shake Curiosity's hand? When? Register your opinion in our unscientific survey above, and voice your views in the comment section below.

More about sending humans to Mars:

• Thousands want to take one-way trip to Mars
• Mars flyby in 2018? It's so crazy it just might work
• NBC News archive on Mars

You can follow the Humans to Mars Summit via streaming video. Check out Explore Mars' channel on Livestream for on-demand videos from Monday's sessions, plus live coverage of Tuesday's sessions.

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

A Martian view from one of Curiosity's hazard avoidance cameras, transmitted back to Earth on Thursday, shows the shadow of the instrument turret on the rover's robotic arm.

NASA's Curiosity rover is back in business after a weeks-long communication gap caused by solar interference. The proof comes in the form of pictures transmitted back to Earth on Thursday from the 1-ton machine's vantage point at Yellowknife Bay on Mars.

"Can you hear me now? Conjunction is over. I have a clear view of Earth & am back to work!" the rover tweeted (with a little help from her entourage at NASA's Jet Propulsion Laboratory).

Dozens of raw images are on display on NASA's Mars Curiosity website, featuring rocky terrain in the foreground and the 3-mile-high (5-kilometer-high) peak known as Mount Sharp or Aeolis Mons in the background. Other Mars probes, including the Opportunity rover, Mars Odyssey and Mars Reconnaissance Orbiter, are back at work as well.

NASA's Red Planet probes were on hiatus for most of April due to an unfavorable alignment of Mars, Earth and the sun. During solar conjunction, the sun gets in the way of the communication lines between the two planets, and mission controllers generally put science operations on hold. Such conjunctions occur every 26 months. Opportunity has gone through several communication breaks during its nine years on Mars, but this is the first one to occur since Curiosity landed last August.

The spacecraft weren't completely idle during the break: Curiosity conducted in-place investigations and sent back limited transmissions via X-band radio to let controllers at NASA's Jet Propulsion Laboratory know that it was doing OK. Opportunity autonomously flipped its computer into safe mode during the break, apparently due to a glitch involving a routine camera check. A fresh set of software commands fixed the glitch, and on Wednesday controllers reported that Opportunity was back in working order.

Curiosity is due for its own software upgrade, and then the rover is scheduled to drill out a second sample of ground-up rock for analysis. The first sample, analyzed in March, suggested that the Yellowknife Bay environment was potentially habitable billions of years ago. Scientists want to use the follow-up sample to confirm what they saw in previous chemical analyses.

After Curiosity finishes up its work in Yellowknife Bay and its surroundings in the Glenelg area of Gale Crater, controllers plan to point the rover toward Mount Sharp, 6 miles (10 kilometers) away. The science team suspects that the mountain's many layers of rock will hold further evidence of ancient organic chemistry.

More about Mars:

• Cosmic Log archive on Curiosity
• Old phallic picture on Mars sparks new titters
• NASA lets poets send haiku to Red Planet

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other 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.

The U.S. government's latest report on the mysterious disappearance of honeybees points to a parasitic mite as the biggest factor behind colony collapse disorder — and downplays the role of controversial pesticides that European officials are planning to ban.

Thursday's report from the Environmental Protection Agency and the U.S. Department of Agriculture says there should be further research into the effects of those nerve-agent pesticides, known as neonicotinoids. But it says the studies so far have not shown it to be the biggest hazard facing the bees.

Last month, beekeepers and environmentalists filed a federal lawsuit calling for an immediate ban on two kinds of neonicotinoids — clothianidin and thiamethoxam. One of the attorneys bringing that suit, Peter Jenkins of the Washington-based Center for Food Safety, told NBC News that his group was "very disturbed" by the way the report was presented, but he also said some of the problems cited in the report supported his case.

'Complex problem'
The report says that a complex combination of causes is behind colony collapse disorder, or CCD, a term that applies to the difficult-to-explain losses that have hit U.S. honeybee colonies since 2006. In the worst cases, entire colonies have disappeared within a few weeks. That's a big problem, because the government says an estimated one-third of all food and beverages are made possible by pollination, mainly by honeybees. Pollination is said to be worth more than $20 billion in agricultural production annually.

The relatively light bee colony losses during the winter of 2011-2012 gave some experts reason to hope that the CCD situation was getting better, but experts say that last winter's losses look as if they were worse than ever.

"The decline in honeybee health is a complex problem caused by a combination of stressors, and at EPA we are committed to continuing our work with USDA, researchers, beekeepers, growers and the public to address this challenge," acting EPA Administrator Bob Perciasepe said in a statement.

Deputy Agriculture Secretary Kathleen Merrigan promised that "key stakeholders will be engaged in addressing this challenge."

Scott Bauer / USDA via AP

A worker bee carries a Varroa mite, visible in this close-up view.

The report draws upon a gathering of officials and stakeholders that took place in Alexandria, Va., last October. It says that the parasitic Varroa mite is the "major factor" behind CCD in the United States and other countries. Varroa mites latch onto the bees and feed on their fluids, weakening the insects. The mites have developed widespread resistance to the chemicals that have been used to control them. The report says more attention should be given to breeding bees that can weather the mites, and notes that gene-sequencing projects focusing on honeybees as well as Varroa mites may provide fresh insights.

Beekeepers have long known about the mite problem, as well as the other causes listed in the EPA-USDA report: poor nutrition, reduced genetic diversity, the Nosema gut parasite, emerging viruses and a bacterial disease called European foulbrood. But figuring out the role played by pesticides has posed the biggest challenge for researchers as well as policymakers.

What to do?
Recent research studies have focused on the effect of neonicotinoids, a neurotoxic type of pesticide that has become widely used because they have little effect on mammals. Most of the studies suggest that the pesticides can scramble a bee's brains — but at what level of exposure?

Some say the exposure levels used in those studies may not accurately reflect the levels that bees experience in the fields. That's the tack taken in Thursday's report: "The most pressing pesticide research questions lie in determining the actual field-relevant pesticide exposure bees receive, and the effects of pervasive exposure to multiple pesticides on bee health and productivity of whole honeybee colonies," it said.

The report says residues from a different class of pesticides, known as pyrethroids, could pose three times as much risk to bees as neonicotinoids.  

The Center for Food Safety's Peter Jenkins complained that the effects of neonicotinoids were being downplayed, but he also called attention to some of the shortcomings mentioned in the federal agencies' report. "They admitted that their labeling is inadequate," Jenkins said. "They admitted that past risk assessments and data requirements were inadequate."

He said some of the proposed policy changes — including, for instance, the introduction of better equipment for coating seed corn with pesticides — would have a positive impact. "What they don't say is that it's going to take years and years to achieve those changes," Jenkins said.

Jenkins called for an immediate tightening of regulations of pesticides. "The one factor that EPA actually has control over is the one that they refuse to regulate," he said.

The EPA is working on a new round of risk assessments for pesticides, but the results of those assessments have not yet been released. Meanwhile, the agency is due to file its response to the environmentalists' lawsuit later this month. Jenkins said Thursday's report would have "no real effect" on the legal action, which could go on for years.

More about the bee die-off:

• Rise in bee deaths stirs up a buzz
• Neonicotinoids tied to crashing bee populations
• Mites and virus team up to wipe out beehives

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other 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.

Canada's new printed-polymer $5 bill has received the country's highest sendoff, altitude-wise, from International Space Station commander Chris Hadfield. Tuesday's currency-unveiling ceremony in space was just the latest in a series of achievements that have drawn attention to Canada's best-known spaceflier.

Hadfield already has made his mark as a photographer, a musician and composer, and an explainer of outer-space phenomena ranging from crying to vomiting in zero-G. There's a reason why the Bank of Canada turned to him to introduce one of the last currency notes to be converted to counterfeit-resistant polymer: One side of the $5 bill celebrates Canada's contributions to space exploration, including the space station's Canadarm2 and DEXTRE robot.

"I just want to tell you how proud I am to be able to see Canada's achievements in space highlighted on our money," Hadfield told Canadian officials via a space-to-Earth video link. Hadfield said the pictures played to Canada's strength in space robotics.

As Hadfield spoke, he plucked a bill from the wall of the station's Destiny laboratory and set it spinning in zero gravity in front of the camera. The other side of the bill has a less spacey theme: It features a portrait of Sir Wilfrid Laurier, who was Canada's prime minister from 1896 to 1911.

Bank of Canada spokeswoman Julie Girard said the outer-space ceremony was "quite a few months in the making." The polymer note was flown up to the space station with Hadfield back in December, and held in reserve for Tuesday's ceremony. "We wanted to be the first to unveil a bank note in space," she told NBC News.

Bank of Canada

This rendition of the Canadian $5 bill shows Canadarm2 and DEXTRE in more detail. The bank note is to be issued in November.

Canada's new $10 note, which commemorates the country's rail system, was unveiled at the same time in Ottawa. The $5 and $10 bills will complete Canada's conversion to polymer-based currency, tricked up with transparent areas and hologram markings to make them harder to counterfeit. The Bank of Canada says these notes should last two to three times longer than the country's cotton-based paper bank notes — and when they wear out, they can be traded in and recycled.

The new notes won't be rolled out to the Canadian public until November. That'll provide enough lead time for training clerks and law enforcement officials to get familiar with the bills. Hadfield will be back on Earth long before November: He's due to get on board the next Soyuz capsule leaving the station on May 14, alongside NASA's Tom Marshburn and Russia's Roman Romanenko.

So what happens to Hadfield's $5 bill? Girard said the astronaut will bring the note down with him, and it will eventually be put on exhibit at the Bank of Canada's currency museum.

Several of Hadfield's priceless photographs of Earth from space are already on exhibit in our latest Month in Space Pictures slideshow. Check out the pictures, plus this bonus 3-D picture of Mars from NASA's Curiosity rover. The 3-D photo was featured in our "Where in the Cosmos" contest on Facebook. Cosmic Log fan Ryan Meader was the first to report that the mountain featured in the picture is referred to as Mount Sharp (by Curiosity's science team) and Aeolis Mons (by the International Astronomical Union).

Meader says he's a long-time reader: "I think it's fair to say that I'm on the hard-core passionate end of the spectrum — so it was to my great delight that I got the jump on this little contest," he wrote.

We're delighted to send Meader a free pair of red-blue 3-D glasses, compliments of Microsoft Research's WorldWide Telescope project — and we'll have a few more spectacles to give away in the weeks to come. So click on the "like" button for the Cosmic Log Facebook page and get ready for the next "Where in the Cosmos" contest.

Slideshow: Month in Space: April 2013

Chris Hadfield / CSA

Feast your eyes on an alligator-like mountain range and other curiosities seen from outer space in April 2013.

Launch slideshow

NASA / JPL-Caltech

A stereo image from NASA's Mars Curiosity rover shows the terrain between the robot and Mount Sharp (a.k.a. Aeolis Mons) inside Gale Crater. Wear red-blue glasses to get the 3-D effect, and don't dwell too much on the hardware in the foreground. Trying to focus in on that part of the picture can make you go cross-eyed.

More about Canada's best-known spaceflier:

• Chris Hadfield's tribute to Boston bomb victims
• What happens to a washcloth in space?
• NBC News archive on Chris Hadfield

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's 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 / SSI

The spinning vortex of Saturn's north polar storm resembles a deep red rose in this false-color image from NASA's Cassini spacecraft. Measurements have sized the eye at a staggering 1,250 miles (2,000 kilometers) across with cloud speeds as fast as 330 miles per hour (150 meters per second). This image was taken from a distance of 261,000 miles (419,000 kilometers) on Nov. 27, 2012, with filters sensitive to near-infrared light.

The eye of a super-hurricane at Saturn's north pole looks like a peaceful red rose in a fresh bouquet of pictures from NASA's Cassini orbiter. But don't be fooled: That rosy appearance is merely due to the false colors ascribed to infrared wavelengths.

This storm's eye measures 1,250 miles (2,000 kilometers) in diameter, about 20 times wider than the average hurricane's eye on Earth. The outer clouds at the hurricane's edge are traveling at 330 mph (530 kilometers per hour), which would be off the scale on our planet. The vortex whirls inside Saturn's mysterious hexagonal cloud pattern, and it's not going anywhere.

"We did a double take when we saw this vortex, because it looks so much like a hurricane on Earth," Caltech's Andrew Ingersoll, a member of the Cassini imaging team, said in a NASA news release on Monday. "But there it is at Saturn, on a much larger scale, and it is somehow getting by on the small amounts of water vapor in Saturn's hydrogen atmosphere."

On Earth, hurricanes are fed by warm ocean water. But there are no oceans on Saturn — so what source drives this super-hurricane? Cassini's scientists want to find out, and whatever they find might add to our understanding of storm dynamics on Earth as well.

The Cassini team suspects that this storm has been active for years, but Cassini has only recently been able to watch it in visible light. When the bus-sized spacecraft arrived in 2004 to begin its $3.5 billion mission to study Saturn and its moons, the north pole was shrouded in winter darkness. Now spring is coming to the north, and Cassini has shifted to an orbit that makes it easier to see the increasingly sunlit storm.

In an email, Cassini imaging team leader Carolyn Porco of the Colorado-based Space Science Institute said the hexagon-ringed vortex is "one of the most gorgeous sights we have been privileged to see at Saturn." But such sights won't last forever: Cassini's extended mission to Saturn is due to end in 2017 with a controlled plunge into Saturn's clouds.

To keep up with the mission in its final years, check in on NASA's Cassini website as well as the online home of the Cassini imaging team, and follow @CassiniSaturn on Twitter.  

NASA / JPL-Caltech / SSI

A false-color image from Cassini highlights the storms at Saturn's north pole. The angry eye of a hurricane-like storm appears dark red, while the fast-moving hexagonal jet stream framing it is a yellowish green. Low-lying clouds circling inside the hexagonal feature appear in a muted orange color. A second, smaller vortex pops out in teal at the lower right of the image. The rings of Saturn appear in vivid blue at the top right. The colors are coded to show different near-infrared wavelengths, which are associated with different altitudes.

Slideshow: Best of Cassini

The Cassini spacecraft is sending back unprecedented imagery of Saturn, its rings and its moons. Click "Launch" to see some of the greatest hits from the Cassini mission.

Launch slideshow

Update for 8:25 p.m. ET April 30: NBC Nightly News anchor Brian Williams found these pictures as awe-inspiring as I did. Here's the video clip:

More beauties from Saturn:

• Venus sparkles in Cassini snapshot
• Seasons change, and so does Saturn
• Cosmic Log archive on the Cassini mission

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up 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.

Slideshow: Month in Space: April 2013

Chris Hadfield / Canadian Space Agency

Feast your eyes on an alligator-like mountain range and other curiosities seen from outer space in April 2013.

Launch slideshow

Mark Greenberg / Virgin Galactic

A bearded Richard Branson (center) gets a congratulatory hug from SpaceShipTwo designer Burt Rutan. Sierra Nevada Corp.'s Mark Sirangelo, who was involved in the development of SpaceShipTwo's hybrid rocket engine, can be seen just to the right of Rutan.

British billionaire Richard Branson's Virgin companies operate airplanes and trains, sell music and phones, offer games and radio shows. He's an adventurer who has flown balloons over oceans, has swum with sharks and whales, and has even started up his own ocean exploration venture. He's had his own reality-TV series and played cameo roles in "Around the World in 80 Days," "Casino Royale" and "Superman Returns." But what really gets the 62-year-old's juices flowing is outer space: Even in a Virgin Mobile TV commercial, Branson's dream of going weightless serves as the kicker.

So it's debatable whether anyone was happier than Branson to see Monday's first blastoff by SpaceShipTwo, the rocket plane that he hopes will take hundreds of regular people (with $200,000 to spend) on quick suborbital trips into outer space. Over the past eight and a half years, Branson has spent tens of millions of dollars to get his Virgin Galactic venture this far, and if the tests continue to go smoothly, he and his kids may soon be getting on the space plane themselves.

Exactly when will that be? Branson's predictions have been uniformly over-optimistic: 2007? 2008? 2012? 2013? Now he says commercial service will start next year. The fact that the future time frame is shrinking suggests that Branson is getting closer to being right. In a quick Q&A, the rebel billionaire talked about the "very long road" behind him and the road that lies ahead:

Cosmic Log: You've talked about how you and your family are looking forward to this. After today's launch, are you looking forward to it even more?

Richard Branson: Of course. It was a thrilling day today. Everything went absolutely according to plan. It looked magnificent. The pilots just loved the experience. I think they were tempted to go straight into space, but knew they'd get fired if they did. We're very much looking forward to getting there either at the end of this year or very early next year.

Mark Greenberg / Virgin Galactic

Virgin Galactic's billionaire backer, Richard Branson, gets a "high-ten" hand-slap from SpaceShipTwo pilot Mark Stucky. George Whitesides, Virgin Galactic's CEO and president, is to Branson's right.

Q: What has this effort meant to you? I don't know if people could have predicted that it would take eight and a half years to get to this point after SpaceShipOne. Has this been a longer road than you thought it would be? Does that make it taste sweeter when things go right?

A: Yes, it's been a very long road. But as far as putting people into space, Virgin Galactic is the only company that has gotten this far. Quite a few other companies have also been working hard to get this far. Today was such an important milestone, in that we knew the rockets were finally working. We knew the spaceship worked on its own. But we obviously needed to test the two together to make sure that the designers got it right. We're absolutely delighted that it broke the sound barrier on its very first flight, and that everything went so smoothly. So we really are on the way now. We've overcome the biggest hurdle, and there are no major hurdles left except for the normal test flights that are needed before we go into space.

Q: How many test flights do you think will be needed? You've already mentioned that you are hoping the first spaceflights could happen by the end of this year, and commercial service would follow. Now that the first powered test has taken place, what does the schedule ahead look like?

A: There will be many test flights between now and the end of the year, before we actually go into space. We'll do as many tests as we feel are necessary before we actually turn it over to myself, my children and other people. We'll be working with the FAA and others to get as many flights under our belts as we feel are needed, but I do think we'll be ready by the end of the year. 

Q: When you saw SpaceShipTwo fire up its engine, were there any surprises, or was it totally the way you expected it to go. Did you ever think to yourself, "Whoa, I didn't think it was going to work that way"?

A: Fortunately, there were no surprises. Until it happens, you have to be nervous, even though you have the best team in the world working with it. What was incredible was how clear it was, just looking up without binoculars. You could visibly see the spaceship getting faster and faster. There's an old saying, "It's not rocket science." But this is rocket science, and that's why it's taken eight and a half years to get this far.

Q: You have more than 500 people who have already put money down for a flight, and many more who are interested in the idea of flying into outer space. What would you say to them about the significance of today's test, and what they can expect in the years ahead?

A: Today was the most significant day in the program. I think that for those people who have been good enough to stick with us for the last eight years, who signed up early on, their time to become astronauts is very soon now. I'd just say, 'Thank you very much for sticking with it.' We'll soon be able to make their dreams come true.

More reactions to the SpaceShipTwo test:

• Charles Lurio, writer of The Lurio Report on private space development: “It’s been a long eight and a half years, but this is the kind of thing that happens in development programs.”
• Commercial Spaceflight Federation: "We are one step closer to achieving safe, routine and cost-effective access to space that will create abundant opportunities for space-based research and that will inspire the next generation of engineers and scientists."
• House Majority Whip Kevin McCarthy, R-Calif.: SpaceShipTwo's supersonic flight is a "major milestone in commercial space travel, bringing us one step closer to offering private commercial space travel and solidifying the Mojave Air and Space Port as our nation’s premier aerospace research, development and test flight center for this emerging space industry."
• Spaceport America: "Today's successful powered flight means we are getting closer to the day when the first Virgin Galactic passenger flight will be taking place from Spaceport America in New Mexico."

More about SpaceShipTwo:

• SpaceShipTwo goes supersonic
• Tom Cruise might be up for space
• Cosmic Log archive on SpaceShipTwo

Slideshow: The making of SpaceShipTwo

Click through scenes from the construction of Virgin Galactic's suborbital passenger spaceship.

Launch slideshow

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

Virgin Galactic's SpaceShipTwo rocket plane lit up its engine for the first time in flight on Monday, taking a giant supersonic leap toward outer space.

The crucial 16-second blast took place at about 7:50 a.m. PT (10:50 a.m. ET), high above California's Mojave Air and Space Port. Virgin Group's billionaire founder, Richard Branson, was on hand to watch the proceedings.

"Today was the most significant day in the program," Branson told NBC News afterward. "I think that for those people who have been good enough to stick with us for the last eight years, who signed up early on, their time to become astronauts is very soon now. ... We'll soon be able to make their dreams come true."

Branson wasn't the only one watching: Rocket aficionados flocked to viewing areas near the airport to see the blastoff. Until Monday, Mojave-based Scaled Composites, which is building and testing the plane for Virgin Galactic's eventual use, had tested SpaceShipTwo only by dropping it from its WhiteKnightTwo carrier airplane and having its pilots guide the plane back through unpowered glides back to the runway. The engine, powered by a rubber-based solid fuel and nitrous oxide, had been fired only on the ground.

Monday's test was radically different: WhiteKnightTwo released SpaceShipTwo from its traditional drop zone, at an altitude of around 47,000 feet. But after the rocket plane glides clear from the mothership, its pilot lit up the engine and pointed SpaceShipTwo upward into the sky, reaching a maximum height of 56,200 feet. The plane coasted back to a landing back at the Mojave airport, about 13 minutes after blastoff.

Test pilots Mark Stucky and Mike Alsbury were at SpaceShipTwo's controls for Monday's flight, Virgin Galactic said. Afterward, the company said in a tweet that the pilots confirmed "SpaceShipTwo exceeded the speed of sound on today's flight!" The reported maximum velocity was Mach 1.2.

Virgin

SpaceShipTwo fires up its rocket engine for the first time in flight on Monday.

MarsScientific.com / Clay Center Observatory

A 16-second rocket blast sends SpaceShipTwo toward the heavens.

Virgin Galactic via W. Christine Choi

A boom camera on Virgin Galactic's SpaceShipTwo plane shows the rocket engine firing.

George Whitesides, Virgin Galactic's president and CEO, said in a news release that the flight test "went as planned, with the expected burn duration, good engine performance and solid vehicle handling qualities throughout."

Eventually, SpaceShipTwo could break the space barrier as well as the sound barrier — just as its predecessor, SpaceShipOne, did in 2004. When the single-piloted SpaceShipOne made repeated flights beyond an altitude of 100 kilometers (62 miles), which is the internationally accepted boundary of outer space, it won the $10 million Ansari X Prize for private spaceflight. Ever since then, Virgin Galactic has been funding the multimillion-dollar development effort to create a fleet of passenger space planes.

In the grand scheme of things, suborbital spaceflight isn't exactly new: The U.S. Air Force's X-15 rocket plane blazed that trail to manned spaceflight a half-century ago. The new twist is that it's being done by private companies rather than government programs. 

Scaled and Virgin Galactic have mapped out a series of flight tests that would gradually push the envelope, potentially leading to suborbital spaceflights over California's Mojave Desert by the end of this year. Virgin Galactic's goal is to begin passenger service, for tourists as well as researchers, at New Mexico's Spaceport America as early as next year. More than 500 people — including celebrities such as Ashton Kutcher — have already put down money for a $200,000 ride.

The six-passenger, two-pilot plane is designed to give riders a commanding view of the curving Earth beneath the black sky of space, a few minutes of free-floating weightlessness, and a roller coaster ride back down to Virgin Galactic's spaceport. Other companies — including XCOR Aerospace and Blue Origin — are planning to get into the suborbital space passenger business as well, but if SpaceShipTwo's flight tests go well, Virgin Galactic is likely to become the market leader.

Branson has said he and his family would be among the first to fill SpaceShipTwo's passenger seats.

"Like our hundreds of customers from around the world, my children and I cannot wait to get on board this fantastic vehicle for our own trip to space and am delighted that today's milestone brings that day much closer," he wrote in a blog post.

Slideshow: The making of SpaceShipTwo

Click through scenes from the construction of Virgin Galactic's suborbital passenger spaceship.

Launch slideshow

More about SpaceShipTwo:

• Virgin billionaire can't wait for space ride
• Tom Cruise might be up for space
• Cosmic Log archive on SpaceShipTwo

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

This story was originally published on Mon Apr 29, 2013 10:29 AM EDT