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.

NASA / GSFC

The MAVEN orbiter, shown in this artist's conception, is to be launched toward Mars in November. NASA is taking names that will be digitized for inclusion on the spacecraft.

Poets, take note: NASA is looking for a few good haiku to send to the Red Planet aboard its MAVEN orbiter this fall.

If you're not the literary sort, don't worry: You can still submit your name to be included on a DVD that will be attached to the spacecraft. MAVEN is scheduled for launch from Cape Canaveral in Florida sometime after Nov. 18. In 2014, it'll go into Martian orbit to study changes in the planet's atmosphere over the course of at least one Earth year. Mission cost is $670 million. MAVEN is short for Mars Atmosphere and Volatile EvolutioN.

Send-a-name opportunities come around at least once every year or so, and they tend to be quite popular with the general public. More than 1.2 million names were collected for the Mars Science Laboratory mission: Those names were etched onto two microchips, each the size of a dime, and then the chips were placed in a protected corner of the Curiosity rover.

This time around, you can submit names via the MAVEN mission's "Going to Mars" website. All the names will be digitized and encoded onto a DVD that will be put on the spacecraft. You can also submit a personal message in the form of a haiku — a traditional form of three-line Japanese verse that has five syllables for the first line, seven syllables for the second line, and five syllables for the third line.

The deadline for submissions is July 1. An online public vote will be conducted beginning July 15 to select the top three haiku poems. Those three poems will be included on the spacecraft as well, and will be prominently displayed on the MAVEN website. Check the "Going to Mars" instructions to get the details and to register your name and message.

"The Going to Mars campaign offers people worldwide a way to make a personal connection to space, space exploration, and science in general, and share in our excitement about the MAVEN mission," Stephanie Renfrow, lead for the MAVEN Education and Public Outreach program at the University of Colorado's Laboratory for Atmospheric and Space Physics, said in a NASA news release announcing the campaign. To put it another way:

Space exploration
blends science and poetry,
blends heaven and earth. 

More about future space missions:

• MAVEN mission prepped for launch
• NASA plans 2020 Mars rover remake
• 13 new space missions for 2013

Alan Boyle is NBCNews.com's science editor (and was editor of his college's literary magazine more than three decades ago). 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.

It's been six long years since world-famous physicist Stephen Hawking got a taste of weightlessness during a zero-G airplane flight from NASA's Kennedy Space Center — but he still wants to feel the real deal aboard Virgin Galactic's SpaceShipTwo rocket plane.

The 71-year-old Hawking has been living with neurogenerative disease for decades, but his illness hasn't kept him from taking on adventures that might tax younger, fitter humans. On Tuesday, during a London talk sponsored by the charity Breathe On UK, Hawking noted that he has required assistance with his breathing since his tracheotomy in 1985.

"Being on a ventilator has not curbed my lifestyle," he told the audience, using his instantly recognizable computer-generated voice. "I have been to Brussels, the Isle of Man, Geneva, Canada, California ... and I hope to go into space with Richard Branson's Virgin Galactic. It is possible to have quality of life on a ventilator."

That's music to the ears of Breathe On UK, which was created to help kids who need long-term breathing assistance. It's also a compliment to Virgin Galactic, which put SpaceShipTwo through its supersonic paces for the first time this week. If all the tests go right, SpaceShipTwo could be taking passengers on suborbital space trips as early as next year.

Richard Branson, Virgin Galactic's billionaire founder, promised to consider Hawking for one of those trips even before the good doctor took his ride into weightlessness in 2007. The invitation still stands, according to George Whitesides, the company's president and CEO.

"Richard and the team would love to welcome him on board," Whitesides told NBC News on Tuesday.

Hawking's health is the big issue for any future spaceflight, just as it was for the zero-G flight years ago. The physicist would have to be fully checked out, and even if he was cleared for takeoff, medical staff would almost certainly have to ride along. Deceleration could be the toughest part of the trip. SpaceShipTwo's flight profile calls for up to 6 G's of force on the way down. That's more force than most space shuttle astronauts have felt, and it ranks right up there with the world's rockiest roller-coaster rides.

If Hawking were to fly into space sometime in the next few years, he'd take the No. 2 spot on the list of the world's oldest astronauts. The only person older would be senator-astronaut John Glenn, who flew on the space shuttle Discovery at the age of 77 and is now 91 years old.

Six years ago, Hawking declared, "Space, here I come!" Should he keep that dream alive, or should he focus on earthly adventures instead? Feel free to register your opinion in our informal survey, and weigh in with your comments below.

More about Stephen Hawking:

• Hawking lays out his case for a godless big bang
• Stephen Hawking visits LA stem cell lab
• Cosmic Log archive on Stephen Hawking

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.

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

Slideshow: Our fragile Earth

AFP - Getty Images

Images from outer space highlight the fragility — and the resilience — of our beautiful blue planet.

Launch slideshow

Technological advances aren't always kind to Mother Earth — witness the impact of nuclear waste, industrial emissions and plastic bottles — but high-tech environmental monitoring systems are also helping us get a handle on the state of our planet. It's good to remember that as Earth Week draws to a close.

Just in the past couple of years, NASA has added to the nation's fleet of Earth-observing satellites. In 2011, the $1.5 billion Suomi NPP satellite went into orbit, blazing a trail for a new generation of planet-watchers that can provide data about extreme weather as well as environmental indicators. Suomi's five sensor systems are tracking atmospheric and sea surface temperatures, biological productivity, ozone levels and much, much more.

This February, the $855 million Landsat Data Continuity Mission finally got off the ground, opening a new chapter for the 41-year-old Landsat Earth-monitoring program. LDCM will monitor surface temperatures around the planet and generate 400 images a day in visible and infrared wavelengths. Multi-wavelength observation is a key technology for monitoring the planet's health, because thermal infrared readings can tell you how vegetation is faring, how much heat the world's cities are putting out, and how the world is coping with climate change.

"If you want to deal with climate, you need observations, instead of just talking about belief or simulations," Compton Tucker, senior biospheric scientist at NASA's Goddard Space Flight Center, told NBC News.

Even Earth's gravity field can provide insights into how the planet is changing: Readings from the Gravity Recovery and Climate Experiment, or GRACE, have traced the loss of ice from the world's glaciers and ice caps by measuring subtle changes in our planet's distribution of mass. "It's really a phenomenal source of information to study water on the surface," Tucker said. 

For decades, observations from outer space — including data from NASA satellites such as Terra and Aqua, as well as the National Oceanic and Atmospheric Administration's weather satellites and the Landsat constellation — have been helping scientists understand what's happening to our environment.

Suomi NPP and LDCM are continuing that legacy, but there are still concerns about the future: Last year, the National Research Council voiced grave concerns about America's aging Earth-observing system, saying that the projected loss of satellite capability "will have profound consequences on science and society, from weather forecasting to responding to natural hazards."

The federal government's money troubles could trigger more immediate cutbacks in the nation's Earth-watching capability. It may well turn out that the biggest obstacles to understanding what ails our planet aren't natural phenomena, but problems of our own making.

More about high-tech environmental monitoring:

• How's Earth's health? New network to keep tabs
• Landsat celebrates 40 years of watching our planet
• How satellites are saving the world

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.

MarsScientific.com / Clay Center Observatory

Cold oxidizer streams from the back of SpaceShipTwo's engine during an unpowered test flight on April 12. Richard Branson, the billionaire founder of Virgin Galactic, says the rocket plane could go supersonic when its engine is lit up for the first time in flight, as early as Monday.

Virgin Galactic's billionaire founder, Richard Branson, says his company is planning to fire up SpaceShipTwo's rocket engine for the first time in flight on Monday — a "historic" blast that is expected to send the space plane supersonic.

"We're hoping to break the sound barrier," Branson told the Las Vegas Sun. "That's planned Monday. It will be a historic day. This is going to be Virgin Galactic's year. We'll break the sound barrier Monday, and from there, we build up through the rest of the year, finally going into space near the end of the year. I'll be on the first official flight, which we look to have in the first quarter of next year. We're doing a number of test flights into space first."

Branson made his comments on Monday during a visit to kick off Virgin America's airline service to Las Vegas. In just one paragraph, the British entrepreneur and adventurer capped off weeks of rumors and laid out a new timeline for starting up passenger flights to outer space.

SpaceShipTwo builds on the heritage of SpaceShipOne, which powered its pilots beyond the 100-kilometer (62-mile) altitude mark in 2004 to win the $10 million Ansari X Prize for private-sector spaceflight. SpaceShipOne is now hanging in the Smithsonian, but SpaceShipTwo has been under development for years at Scaled Composites in Mojave, Calif. Scaled has been conducting a series of unpowered tests at the Mojave Air and Space Port. During an April 12 "cold flow" flight test, Scaled's pilots rehearsed every step for a powered flight, short of lighting up the hybrid rocket engine.

So far, SpaceShipTwo has been attached to the belly of its WhiteKnightTwo mothership, carried up to altitudes of around 50,000 feet and then dropped into the air to make a glider-like landing. During powered tests, SpaceShipTwo's engine will be lit up after the drop. The rocket plane will make a spectacular blast into the heavens and then glide back to the runway.

"We’ve experienced about a year’s worth of vertical flight tests and captive-carry flight tests by a number of tenants, and now we’re entering the phase of manned research flights," Stuart Witt, CEO of the Mojave Air and Space Port, told NBC News. "We’re excited about that: The industry has been waiting for this for a long time – since 2004."

Virgin Galactic's CEO and president, George Whitesides, stressed that the test schedule was dependent on several factors, including the weather. He said the first rocket-powered test could easily slip to a later time.

Like Branson, Whitesides said the first powered flight, known as PF01, would be merely the first step in the next phase of testing. "PF01 will be the start of a series of increasingly longer-duration burns (PF02, PF03, etc.) that should lead us to space altitude before the end of the year and commercial ops start soon after that," he said in an email to NBC News.

Virgin Galactic plans to conduct commercial spaceflights from Spaceport America in New Mexico, with passengers charged $200,000 for a ride. More than 500 customers have already put money down for flights. The passengers would experience breathtaking views of the curving Earth beneath the black sky of space, go weightless for a few minutes and then strap themselves back in for a powerful plunge back to the runway.

The first supersonic flight of a new spaceship isn't always auspicious: When SpaceShipOne came in for a landing in Mojave after breaking the sound barrier for the first time on Dec. 17, 2003, its left landing gear collapsed and the plane ran off the runway. Fortunately, no major damage was done, and pilot Brian Binnie was unhurt. Binnie went on to fly SpaceShipOne into space on Oct. 4, 2004, to win the $10 million prize.

Blue Origin, a rocket venture backed by Amazon.com billionaire Jeff Bezos, put its prototype spacecraft through its first unmanned supersonic flight at a Texas rocket range in August 2011 — but the company said the craft had to be destroyed when it experienced a "flight instability" at an altitude of 45,000 feet. Blue Origin recovered from that setback and is continuing to work on suborbital as well as orbital spacecraft.

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 as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email inbox 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 / Cornell

When some people look at this nine-year-old picture from NASA's Spirit rover, they see a graphic depiction of manhood. Actually, it's standard operating procedure for making a turn on Mars.

Some Mars maniacs just won't grow up: A picture of the track patterns left behind by the Mars rovers' standard turning maneuver has drawn giggles and gasps — merely because it looks like a penis scrawled on the Red Planet.

"The rude drawing has emerged in a series of images taken by one of its rover machines. ... The latest pictures beamed back from one of the rovers show signs that the project's controllers have started to get a bit bored," The Sun, a British tabloid, reported on Wednesday.

Even Sarcastic Rover, one of Twitter's top parody personas, got into the act: "Since everyone's asking, let me just say that some other robot did this ... definitely not me," it tweeted.

The jibes from Sarcastic Rover and The Sun, and tons more like them, were sparked by a Reddit forum's discovery of the picture the day before. But this picture isn't the product of a bored (or filthy-minded) rover driver, and it wasn't beamed down recently. It's part of a classic nine-year-old panorama from NASA's Spirit rover, looking back toward its landing platform. (You can actually see the platform in the high-resolution version of the panorama.)

This type of rover wheel-track pattern, which could euphemistically be called "a bat and two balls," has been left on Mars many times, not only by Spirit (which gave up the ghost in 2010 or so), but also by Opportunity (which is still going strong more than nine years after landing on Mars) and Curiosity (which landed last year).

All those rovers have six wheels, three on each side, and they leave behind two parallel tracks when they're traveling in a straight line. When the rover has to make a turn, the wheels rotate in place to put the robot in the desired direction for the next leg of its trek. If the turn is significant enough, you get a nice set of circles at the end of a pair of parallel tracks.

Got it? Now we can move on — for instance, to lewd pictures from the Hubble Space Telescope.

NASA / ESA / STScI / AURA / La Plata Obs.

A sub-cloud of dust in the Carina Nebula displays what some have called "the cosmic finger of friendship."

More tracks from the Red Planet:

• That's one small step ... on Mars?
• Curiosity leaves tracks in Morse code
• 3-D adds depth to tracks on Mars

Tip o' the Log to Jia-Rui Cook at NASA's Jet Propulsion Laboratory for finding the original Spirit panorama from Mars.

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.

What will the far future look like? For actor Will Smith and his son Jaden, the next generation could mark a "tipping point" for the environment. For futurist Ray Kurzweil, solar power is the solution to our energy ills. But for a look at the really far future, turn to Elon Musk, the billionaire founder of SpaceX and Tesla Motors. He's already thinking about spreading out from Earth to other planets — and engaging the warp drive to get to other star systems.

"There's some potential, even though it sounds science-fictiony, for warp drive to work," Musk said on Tuesday during a Google+ Hangout to publicize "After Earth," Smith's upcoming movie. "Technically, to warp space such that you're traveling at the speed of light, but you've warped space so that space is actually traveling."

Musk was referring to recent studies updating the "Star Trek" conception of warp travel, in which a whole region of the space-time continuum zips along at faster-than-light speeds. Researchers at NASA's Johnson Space Center say the idea isn't as crazy as it sounds, and they're trying to create space-time perturbations on a microscopic scale.

Even NASA Administrator Charles Bolden is on board: "One of these days, we want to get to warp speed," he said last September. "We want to go faster than the speed of light, and we don't want to stop at Mars."

Musk, however, sees Mars as a key stop on the path to turning humanity into a multiplanet species. "Either we're a spacefaring civilization, or we're going to be bound to Earth until some eventual extinction event," he said Tuesday.

All this meshes with the plot of "After Earth," in which Will and Jaden Smith play a father and son who find themselves back on Earth a millennium after cataclysmic events forced humanity to find refuge in a distant star system. The filmmakers organized the Hangout to give the Smiths as well as Musk, Kurzweil and environmentalist Alexandra Cousteau a chance to reflect on humanity's future. (It was also a chance to give the movie some publicity on the day "after Earth Day.")

You can watch the whole Hangout on YouTube, but here are some highlights:

Will Smith on working with his son on the movie: "It was wonderful for the two of us to become environmentally educated together. ... The huge question of water came up: the idea that today it's oil that we're willing to go to war over, and at some point in the future, it's going to be water."

Jaden Smith, 14, on the challenges facing the next generation: "Our world is going to get to a tipping point ... if we want to stop that, then my generation would have to almost become obsessed with it, and say we're stopping everything that we're doing wrong right now: no more plastic, only reusable sources, only solar power."

Alexandra Cousteau, granddaughter of Jacques-Yves Cousteau: "We're on the knife's edge of either protecting this place where we live, or losing an enormous amount of it. But I have to say I completely agree with Jaden, in that this generation has an extraordinary opportunity to use technology that we've never had before ... to actually take control of our use of resources."

Ray Kurzweil, Google's director of engineering, on the promise of solar power: "The total solar energy in the world is on an exponential rise. It's doubling every two years. ... Within 15 years we could meet all of our energy needs with solar. Solar is actually cost-comparative with other forms of energy like fossil fuels without any subsidies in different regions of the world."

More thoughts on the future: 

• Engineering's greatest challenge: our survival
• Take a test drive through the next century
• The biggest challenge for interstellar flight? Us

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.