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.

M. Showalter / NASA / ESA

An image from the Hubble Space Telescope shows Pluto and its largest moon, Charon, surrounded by four smaller moons. Astronomers have proposed naming P4 and P5 after Vulcan and Cerberus.

Astronomers have decided to go with the people's choice and propose Vulcan and Cerberus (or Kerberos) as the names for Pluto's tiniest known moons, one of the discovery team's leaders said Tuesday. Vulcan bubbled up to the top of the list in a non-binding "Pluto Rocks" contest in February, thanks in part to a strong endorsement from "Star Trek" captain William Shatner. The International Astronomical Union, which traditionally approves celestial names, still has to weigh in on the discoverers' proposal.

"We did not feel rigidly bound by the vote totals, but in the end we decided that Vulcan and Cerberus/Kerberos were pretty good names," said Mark Showalter, a planetary scientist at the SETI Institute who organized the contest. Showalter discussed the selection process in an email to NBC News after Nature reported that the IAU was considering the names.

Shatner, who played Captain James T. Kirk on the original "Star Trek" series, proposed the name Vulcan in honor of the home planet of Kirk's pointy-eared science officer, Mr. Spock. He put out the word to more than a million Twitter followers, and Vulcan ended up receiving 174,062 of the 450,324 votes cast. Cerberus was No. 2 on the list, with 99,434 votes.

Astronomers needed two names — one for the Plutonian moon P4, discovered in 2011; and another for P5, found in 2012. Although Vulcan and Cerberus were the favorites, it was not assured that the discovery team would go with those choices.

Stating the case
Traditionally, Pluto's moons are named after figures of the underworld from Greek or Roman mythology. Cerberus fit that scheme, because that was the name of the dog that guarded the gates of the Greco-Roman underworld. Vulcan, which is the name of the Roman god of fire as well as Mr. Spock's home world, posed more of a challenge.

"For the IAU proposal, I had to make the connection between Vulcan and the Greco-Roman underworld, because I knew that the nomenclature working groups would not be swayed by Star Trek mythology," Showalter explained. "We don't normally associate Vulcan with Pluto, but in fact when you go back to the literature, the Greeks and Romans understood the underworld to encompass everything beneath the surface of the earth, not just the realm of the dead. So Vulcan, the god of lava and volcanoes, really does have a natural connection to underworld.

"That being said, the nomenclature working group has to grapple with the issue that in astronomy, the name Vulcan has previously been associated with a hypothetical object or objects orbiting interior to Mercury. They also will probably have concerns about the fact that Cerberus has already been used as the name of an asteroid. I still believe that it is very important to give the working group latitude in this decision. I remain optimistic that a consensus will emerge."

One possibility would be to use Kerberos as an alternate spelling for Cerberus, to avoid any potential confusion. That's how the discoverers of another moon of Pluto, Nix, got around the fact that there was already an asteroid named after Nyx, the Greek goddess of the night.

Nicknaming an exoplanet
Meanwhile, another celestial naming contest has come to a surprise ending. For weeks, a commercial venture called Uwingu has been running a contest to come up with an unofficial nickname for Alpha Centauri Bb, the closest exoplanet. Thanks to a last-minute surge of vote-buying, the winner of the planet-naming game is "Albertus Alauda."

"I chose this name to honor my grandfather," Jason Lark wrote in his online citation for the name. He explained that Albertus Alauda is the Latin translation of Albert Lark, his grandfather's name.

Uwingu charges $4.99 for each planet nomination, and 99 cents for each vote. A spokeswoman for Uwingu, Ellen Butler, told NBC News in an email Tuesday that Lark "came in with a $742.50 payment last night to take the win." The mass voting is perfectly in accordance with the rules of Uwingu's game.

"I am overjoyed that my nomination won," Lark told NBC News in an email. "I think my grandfather would be very happy, and I hope my citation does him justice. I am very proud of my granddad. As with any other star or planet, they along with their names live on much longer than any one man, and most have a story behind them, such as in the days of old when stars were used to navigate the globe. I would like to think that Albertus Alauda will take its place alongside them in the generations to come, along with the story behind it."

Uwingu was created last year to offer space-based entertainment, to generate revenue and raise money for space science and education projects. The aim is to distribute at least half of the proceeds in the form of grants to programs such as the SETI Institute's Allen Telescope Array, Astronomers Without Borders and the Galileo Teacher Training Program. The contest to nickname Alpha Centauri Bb, which was discovered last year just 4.3 light-years from Earth, brought in about $10,000.

Among the runner-up names were Sagan and Einstein, Ron Paul and Heinlein, Rakhat (the Alpha Centauri planet featured in a sci-fi novel called "The Sparrow"), Tiber (the Alpha Centauri planet that moonwalker Buzz Aldrin made famous in his novel "Encounter With Tiber") and Amara (the first name of the nominator's fiancee). In all, more than 1,200 names were nominated.

Neither Albertus Alauda nor any of those other names has official status with the IAU. In a stinging news release, the IAU said Uwingu's campaigns "will not lead to an officially recognized exoplanet name, despite the price paid or the number of votes accrued."

There is currently no IAU-sanctioned process for approving popular names for the hundreds of extrasolar planets detected beyond our solar system. Instead, astronomers take the name of the star (for example, Alpha Centauri B or Kepler-62) and tack on a letter of the alphabet, starting with "b." (Hence, Alpha Centauri Bb or Kepler-62f.) For the time being, the IAU is sticking with that system, although it said members would discuss establishing a friendlier naming scheme this year.

Meanwhile, Uwingu's "baby book of names" for exoplanets remains open for business. "Also, next week we'll debut a new way to engage in exoplanet naming," Uwingu's CEO, planetary scientist Alan Stern, said in an email.

More about exoplanet names:

• Who gets to name alien planets?
• Newfound planets need better names
• Why Pluto can't have a Mickey moon

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.

J.-Y. Li (PSI) / NASA / ESA

Comet C/2012 S1 (ISON) takes on a fuzzy glow in an April 10 image from the Hubble Space Telescope. The blue tint has been added to the black-and-white imagery.

Comet ISON, the long-traveling iceball that skywatchers hope will turn into the "Comet of the Century," takes on a fuzzy glow in an image captured two weeks ago by the Hubble Space Telescope and unveiled on Tuesday.

The picture was taken on April 10, using Hubble's Wide Field Camera 3, when the comet was 386 million miles (621 million kilometers) from the sun and 394 million miles (634 million kilometers) from Earth. That's just inside the orbit of Jupiter. Right now, the comet's brightness is roughly magnitude-16, which means it can only be seen with telescopes. But comet-watchers are hoping that ISON will get dramatically brighter as it swings around the sun in late November. Some have said the comet could match the brightness of Venus or even the full moon.

The reason for those hopes — and the reason for all the "coulds" and "mights" — is that ISON appears to be a long-period comet, coming in from the far reaches of the solar system for the first time in living memory. Such comets are unpredictable: Will they shed lots of dust and glowing gas, or will they turn out to be duds? ISON's orbit is due to bring it within 700,000 miles (1.2 million kilometers) of the sun's surface. That could cause ISON to crumble like Comet Elenin did in 2011, or it could spark a flare-up of Comet Lovejoy proportions.

Unlike Comet Lovejoy, which lit up the Southern Hemisphere's skies during 2011's holiday season, Comet ISON should be visible from the Northern Hemisphere — which means Americans might get an eyeful during this year's winter holidays. (There's that pesky "might"!)

The picture from Hubble helps astronomers get a better fix on the current state of Comet ISON: The nucleus appears to be no larger than three or four miles (five to seven kilometers) across. In Tuesday's image release, the Hubble team says that's "remarkably small, considering the high level of activity observed in the comet so far." The comet's fuzzy head, known as the coma, measures about 3,100 miles (5,000 kilometers) across, or a little less than the distance from New York to Dublin. ISON's tail extends more than 57,000 miles, far beyond Hubble's field of view.

Detailed readings from Hubble could unlock the secrets of ISON's origins, University of Maryland astronomer Michael A'Hearn said in a news release. "We want to look for the ratio of the three dominant ices, water, frozen carbon monoxide, and frozen carbon dioxide, or dry ice," A'Hearn said. "That can tell us the temperature at which the comet formed, and with that temperature, we can then say where in the solar system it formed."  

Comet ISON was discovered last September and is formally known as C/2012 S1 (ISON). It takes its name from the International Scientific Optical Network, a group of observatories in 10 countries managed by Russia's Keldysh Institute of Applied Mathematics.

J.-Y. Li (PSI) / NASA / ESA

This contrast-enhanced image was produced from Hubble's view of Comet ISON to reveal the subtle structure in the inner coma of the comet. Such enhancements help astronomers determine the comet's shape and evolution, plus the spin of its solid nucleus.

More about comets:

• Moon and Comet PanSTARRS pair up
• Flash interactive: Inside a comet
• Cosmic Log archive on comets

The image was created from Hubble data from proposal 13198: J.-Y. Li (Planetary Science Institute), P. Lamy (Laboratoire d'Astrophysique de Marseille), H. Weaver (JHU/APL), M. A'Hearn and M. Kelley (University of Maryland), M. Knight (Lowell Observatory), T. Farnham (University of Maryland), and I. Toth (Hungarian Academy of Sciences).

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.

Thermal-imaging devices have been used to seek out pot-growing operations, map Martian geology — and now, to watch the second suspect in this week's Boston Marathon bombings as he was holed up in his last hiding place.

Authorities said a helicopter equipped with a thermal imager spotted the heat signature of a person inside a tarp-covered boat, sitting in a backyard in Watertown, Mass. Police used the sensor after an area resident reported seeing a trail of blood leading to the boat — and catching a glimpse of a blood-covered body inside. The thermal readings confirmed that there was indeed someone under the tarp, and that the person was still alive.

"Our helicopter had actually detected the subject in the boat," Col. Timothy Alben of the Massachusetts State Police told reporters. "We have what's called a FLIR — a forward-looking infrared device — on that helicopter. It picked up the heat signature of the individual, even though he was underneath what appeared to be the 'shrink wrap' or cover on the boat itself. There was movement from that point on. The helicopter was able to direct the tactical teams over to that area."

There was an exchange of gunfire when a SWAT team approached the boat, so police had to back off. The helicopter continued to track the body's movements inside the boat. Eventually, the tactical team moved in and took the wounded bombing suspect, 19-year-old Dzhokhar Tsarnaev, into custody.

How thermal imaging works
Thermal imagers can spot the signature of a heat source inside a house, a vehicle, or in this case, a vessel. Walls may stop visible-light wavelengths, but the heat can still pass through. Variations in heat emissions can be picked up by camera chips designed to be sensitive to the infrared part of the spectrum. The signature would be particularly noticeable when there's a significant difference between the background temperature and the temperature of the heat source.

Police have long used such devices to find out whether marijuana was being grown inside a house using heat lamps. In 2001, the Supreme Court ruled that the use of thermal scans to monitor heat sources inside a person's home should be considered a "search" under the Fourth Amendment, and thus would require a warrant. The court said such scans could reveal private details about the homeowner, including the time of night when "the lady of the house takes her daily sauna and bath."

Thermal imagers have been taken to other worlds — for instance, aboard NASA's Mars Odyssey orbiter, which analyzes variations in the composition of the Red Planet's surface using the Thermal Emission Imaging System, or THEMIS.

Immigration authorities have used thermal scanners to look for the signs of fever among arriving passengers, and researchers have been experimenting with them as a lie-detector technique.

In 2009, FBI investigators used thermal imagers to search for graves in the neighborhood where Cleveland serial killer Anthony Sowell lived. That may well have been the most notorious case where the technology was brought to bear. Until now.

Update for 5:43 p.m. ET April 20: The comments on this story might suggest I've shed more heat than light on the role played by thermal imaging. There's no question about it: The crucial break in the case came when the boat owner, David Henneberry, saw the blood-covered body in the boat, called police and then got out of the way. Police used thermal imagery to track the suspect's movements inside the boat, and help guide the SWAT team's response.

In most cases, thermal imagers can detect only the heat signature emanating from a wall or a vehicle. For example, you could tell whether there were heat lamps (or a lady taking a bath) in a particular room by noticing the high level of heat emitted by the room's walls. But you generally wouldn't see the outline of the heat lamps themselves (or the lady, for that matter). In the Cleveland serial-killer case, thermal imaging was used to look for the signs of freshly turned soil rather than for the cold, dead bodies themselves.

The Watertown case is special: The tarp was so thin that police could indeed see Tsarnaev's outline, as graphically illustrated by these pictures.

More about thermal imaging:

• PhotoBlog: More thermal images of suspect
• Infrared holography identifies fire victims
• Like Pinocchio, your nose shows when you lie
• New tech gives soldiers Predator-style vision

Slideshow: Search for suspects in Boston Marathon bombings

Jared Wickerham / Getty Images

Cheers filled the streets after a Boston Marathon bombing suspect was captured alive but wounded Friday night — following a daylong manhunt that shut down the city.

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 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 Fri Apr 19, 2013 9:14 PM EDT

NASA / ESA / AURA / STScI

The Horsehead Nebula shines in a Hubble Space Telescope image that marks this month's 23rd anniversary of the orbiting observatory's launch.

Astronomers have come out with a Horsehead Nebula of a different color to celebrate the Hubble Space Telescope's 23rd birthday.

The iconic nebula in the constellation Orion, about 1,500 light-years away, can be seen even through small telescopes. In visible light, it's a dark dust cloud in the shape of a horse's head, silhouetted against a backdrop of glowing hydrogen gas. But the Horsehead takes on a completely different look in the new view released Friday.

"This image was taken in the infrared," Joe Liske, an astronomer from the European Southern Observatory, explains in a video introducing the picture. "In infrared light, we can pierce right through some of the bulky plumes of dusty material which usually mask and obscure the inner regions of the Horsehead. The result is this rather fragile-looking structure, made of delicate, wispy folds of gas — very different to the nebula's appearance in the visible."

The infrared glow, captured by Hubble's Wide Field Camera 3, lights up the nebula's clouds from within. Liske says it's "a fitting celebration of an incredible 23 years of the NASA/ESA Hubble Space Telescope."

The Hubble team traditionally releases an eye-popping shot to celebrate the anniversary of the space telescope's launch on April 24, 1990. As part of this year's celebration, the Hubble Heritage Project asked astronomers around the world to send in their own Horsehead Nebula photos, and you can see the collection via Flickr and Tumblr.

Like a veteran racehorse, Hubble is hitting its stride — but that hasn't always been the case. The first couple of years of operation were hampered by a flaw in the telescope's main mirror. Equipment to compensate for the problem was installed during a crucial series of spacewalks 20 years ago, in 1993. The shuttle Atlantis paid a final servicing visit to Hubble in 2009, and the telescope has been working just fine since then.

Hubble operations have been extended through 2016 — and if the telescope remains in good working order, it's likely to continue being funded at least until 2018, when the $8.8 billion James Webb Space Telescope is scheduled for launch. Eventually, Hubble will have to be sent down to a fiery doom. But who knows? Maybe the old telescope will hang around to experience life after 30.

Slideshow: Classic Hubble Hits

NASA / ESA / STSI via Reuters

See the Hubble Space Telescope's best-known images.

Launch slideshow

More Hubble birthday gifts:

• 22 years: Panorama of the Tarantula Nebula
• 21 years: Raise your glass for Hubble's birthday
• Cosmic Log archive on Hubble Space Telescope

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.

We've recently been reminded about the problems posed by zero-G poop and weightless weeping, but here's a real puzzler for zero-G hygiene: What happens to the water when you wring out a washcloth on the International Space Station? That's the question addressed in Canadian astronaut Chris Hadfield's latest silly science experiment  — and the answer might not be what you expect.

This experiment takes the prize ... literally: It was designed by Kendra Lemke and Meredith Faulkner, two 10th-graders at Lockview High School in Fall River, Nova Scotia, and entered in a science contest sponsored by the Canadian Space Agency. A panel of judges selected the "Ring It Out" demonstration as the contest's winner.

Would the water spray out in a hail of fast-moving droplets, or blurp out in slow-moving globs? Actually, the students hypothesized that the water would just stay on the washcloth — and Hadfield proved them correct during Tuesday's live demonstration.

"The experiment worked beautifully," Hadfield said. "The answer to the question is, the water squeezes out of the cloth, and then because of the surface tension of the water, it actually runs along the surface of the cloth and then up into my hand, almost like you had gel on your hand, and it'll just stay there. Wonderful moisturizer on my hands."

It's one thing to read those observations, and quite another to see them on video. Watch the experiment, and then dig into these other hot topics in zero-G hygiene:

More about life in space:

• Better not cry in space
• Poop in space revisited
• How not to be a space slob
• How to cope with space scares

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's Kepler planet-hunting probe has identified two potentially habitable planets only a little bigger than Earth, circling a star that's 1,200 light-years away. The planets could conceivably be covered by a global ocean, and they may well lead the growing list of alien worlds that can host life as we know it.

"These two planets are our best candidates for planets that might be habitable," said Bill Borucki, a space scientist at NASA's Ames Research Center who is the principal investigator for the $600 million Kepler mission.

The two habitable-zone planets, Kepler-62e and Kepler-62f, are part of a five-planet system that lies in the constellation Lyra, within a patch of sky that's been monitored by the Kepler space telescope over the past four years. The Kepler-62 parent star is about two-thirds the size of our own sun and about a fifth as bright.  Three of the star's confirmed planets circle the star in orbits so close that they'd be too hot for life. But the e and f planets are considered to lie in a zone where liquid water could exist, a ring of space that's defined as the habitable zone.

Water worlds?
Two members of the Kepler science team say their modeling suggests the two planets could be "water worlds" — with no land in sight.

"These planets are unlike anything in our solar system. They have endless oceans," Lisa Kaltenegger, an astronomer at the Max Planck Institute for Astronomy and the Harvard-Smithsonian Center for Astrophysics, said in a news release. "There may be life there, but could it be technology-based like ours?"

The report on the Kepler-62 system was published online on Thursday by the journal Science, and was the focus of a NASA news conference timed to coincide with publication. The water-world analysis, authored by Kaltenegger and Harvard's Dimitar Sasselov and Sarah Rugheimer, is contained in a separate paper that has been accepted for publication in The Astrophysical Journal.

The characterization of the two planets' habitability is based on an analysis of their size, plus what's known about the parent star. The Kepler data can show how wide a planet is, and how quickly it makes its orbit, by analyzing the telltale dips in light as the planet passes over its parent star. But Kepler can't make direct observations of a planet's mass. So, in Kepler-62's case, scientists had to make educated guesses about the planets' mass, composition and whether they had atmospheres.

Kepler-62e is 1.6 times as wide as Earth and orbits its star every 122.4 Earth days. Kepler-62f is 1.4 times Earth's width, with an orbital period of 267.3 Earth days. "It's highly likely they're rocky planets," Borucki told NBC News. "They might be water worlds, but they are so different, we just don't know."

David A. Aguilar / CfA

This artist's conception shows Kepler-62f as an ice-covered world, and Kepler-62e as an Earthlike planet with dense clouds. Other planets follow closer-in orbits and are not considered habitable.

NASA Ames / JPL-Caltech

The diagram compares the planets of the inner solar system to Kepler-62, a five-planet system about 1,200 light-years from Earth in the constellation Lyra. The five planets of Kepler-62 orbit a star classified as a K2 dwarf, measuring two-thirds the size of the sun and one-fifth as bright.

What would life be like?
Astrobiologists say the fact that the planets are bigger than Earth wouldn't be an obstacle for life. In fact, some experts argue that a super-Earth is more likely to have life than an Earth-sized planet. "If you and I walked on it, our weight would double," Borucki said. "But my weight has doubled since I was a teenager ... so we could do it."

If the planets had atmospheres like Earth's, Kepler-62e's surface temperature would be 86 degrees Fahrenheit (30 degrees Celsius), while Kepler-62f's temperature would be 19 degrees below zero F (-28 degrees C), Borucki said. "You'd see the sun being substantially larger than our sun, because it's so much closer," he said. "But it'd be darker, like walking around on a cloudy day."

In their research paper, Kaltenegger and Sasselov assume that Kepler-62e has a slightly cloudier atmosphere than Earth's, and that Kepler-62f has a thick carbon-dioxide atmosphere with a strong greenhouse effect. Without a thick atmosphere, Kepler-62f could get chillier than Mars. It might even look more like a Europa-style iceball than a Kevin Costner-style water world.

"Kepler-62e probably has a very cloudy sky, and is warm and humid all the way to the polar regions," Sasselov said. "Kepler-62f would be cooler, but still potentially life-friendly. The good news is, the two would exhibit distinctly different colors and make our search for signatures of life easier on such planets in the near future."

Habitable worlds ahead
Kepler-62e and Kepler-62f aren't the first habitable-zone planets to be identified by the Kepler team, and they won't be the last. A year and a half ago, Kepler-22b came to light as the mission's first potentially habitable planet. It's 2.4 times wider than Earth, which puts it halfway between our planet and Neptune on the size scale. Kepler-47c, unveiled last year, is also a habitable-zone planet — but it's 4.6 times wider than Earth, which makes it Neptune-sized.

This January, the science team discussed the habitability of another candidate planet, then known as KOI 172.02. The existence of that world has now been confirmed under the name Kepler-69c, with a size that's 1.7 times Earth's width. "Today we can announce that this is a bona fide planet," Thomas Barclay, an astronomer at Ames Research Center, said during Thursday's news conference. 

Three months ago, Kepler-69c was hailed as potentially the most Earthlike world detected beyond our solar system, but now researchers say Kepler-62e and Kepler-62f could be stronger contenders.

There will be more contenders ahead: Borucki said about four dozen of the more than 2,700 candidate planets being tracked by Kepler lie within their stars' habitable zones, and it takes about a year to confirm each candidate's existence through detailed analysis. "We really wish we were faster," he told NBC News. "I really wish we could knock off one a week."

Boruckin and his colleagues are poring through the oceans of observations coming in from the Kepler telescope, and although the spacecraft has had its problems, he's hoping that the flood of data will continue for years to come.

"When you're born a scientist, they leave out the gene for saying, 'We have enough data,'" Borucki joked.

More about the planet hunt:

• Alien Earths in our backyard?
• 17 billion hot Earths in our galaxy
• NBC News on planets | Cosmic Log on Kepler

Borucki, Kaltenegger, Sasselov and Barclay are among 64 authors of the Science paper, "Kepler-62: A Five-Planet System with Planets of 1.4 and 1.6 Earth Radii in the Habitable Zone." Barclay and Borucki are among 31 authors of "A Super-Earth-Sized Planet Orbiting in or near the Habitable Zone around Sun-like Star," published in The Astrophysical Journal. Kaltenegger, Sasselov and Rugheimer are the authors of "Water Planets in the Habitable Zone: Atmospheric Chemistry, Observable Features, and the Case of Kepler-62e and -62f."

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 / JPL-Caltech / MSSS

This graphic shows the relative sizes of Earth, Mars and Europa, an icy moon of Jupiter.

A British astrobiology conference has revived a years-old debate over the best place to look for life elsewhere in the solar system: Mars, or the moons of Jupiter and Saturn?

"For reasons I don't really understand, the wider solar system and the potential for life there has not been high priority," The Telegraph quoted Robert Pappalardo, a senior research scientist at NASA's Jet Propulsion Laboratory, as saying on BBC Radio 4.

Pappalardo's remarks were occasioned by this week's astrobiology conference at the UK Center for Astrobiology in Edinburgh, Scotland. The center recently established the International Subsurface Astrobiology Laboratory, or ISAL, half a mile (1 kilometer) beneath the surface in Yorkshire's Boulby mine. Biologists will use that facility to see how organisms hold up in extreme environments, learn about life's chemical signatures, and test instruments that could look for those signatures on other worlds.

Someday, one of the worlds may well be Europa, an icy moon of Jupiter. With a diameter of 1,945 miles (3,130 kilometers), Europa is just slightly smaller than Earth's moon, and yet it is thought to contain more water than Earth's oceans beneath a miles-deep layer of ice. Researchers recently suggested that hydrogen peroxide in the ice could serve as an energy supply for simple forms of life in the ocean hidden below.

Europa is the focus of Pappalardo's research, and for months he has been urging NASA to support a $2 billion mission to study Europa at close range. However, proposals for NASA missions to Europa have been losing out, in part because of the cost of missions to Mars. Last week's federal budget proposal for the next fiscal year provides no funding for a Europa mission, but it does fund Mars missions such as Maven (launching this year), InSight (launching in 2016) and a new science rover (launching in 2020).

Kevin Hand (JPL-Caltech) / Jack Cook (WHOI) / Howard Perlman (USGS)

If Europa's ocean is 100 kilometers (62 miles) deep, and all that water were gathered into a ball, it would have a radius of 877 kilometers (545 miles). This graphic compares that hypothetical ball of Europan water to the size of the Jovian moon itself, as well as all the water on planet Earth. Europa is thought to have two to three times the volume of water in Earth's oceans.

At February's annual meeting of the American Association for the Advancement of Science, Pappalardo worried that NASA's study of the outer solar system would go "radio-dark" in 2017, when the Cassini mission to Saturn and the Juno mission to Jupiter are both due to end. He continued that theme in this week's BBC interview.

"I worry that if Europa exploration is delayed, but then finally it happens some day, we might look back and say 'Why didn't we do that sooner?' Imagine 50 years from now, we get a lander there and find signs of life. All this time we'll have been looking in the wrong place," he was quoted as saying.

Europa isn't the only moon that intrigues astrobiologists: In the Jovian system, Callisto and Ganymede also have icy shells and may hold hidden oceans. Meanwhile, Cassini has repeatedly observed geysers of water ice rising from the surface of the Saturnian moon Enceladus — suggesting that liquid water and perhaps life may lie beneath the surface. Saturn's largest moon, Titan, has a thick atmosphere and seas of hydrocarbon that some scientists think could harbor a totally alien kind of life.

As for Mars, astrobiologists say hints of life could well lurk beneath the surface. To some extent, the Red Planet has been winning out over Europa and Enceladus because it's easier to get to. Moreover, NASA's vision calls for sending astronauts to Mars and its moons in the 2030s. NASA's robotic missions serve as precursors for those human voyages, as well as steps in a long-term program to learn about life in the universe.

Europa's fans can take heart in the fact that the European Space Agency is planning its own mission to Jupiter's moons: The Jupiter Icy Moons Explorer, or JUICE, is due for launch in 2022 and arrival at the Jovian system in 2030. There's also talk of a sample return mission that would target Enceladus' geysers, and a proposal to drop a boat onto Titan's seas.

So what if all of these worlds — Mars and Europa, Callisto and Ganymede, Titan and Enceladus — turn out to be lifeless? Charles Cockell, who heads the UK Center for Astrobiology, addressed that scenario in an interview with the BBC.

"A lot of people think astrobiology is some sort of hunt for life, and if we don't find life, it will be a big disappointment," Cockell said. "But in fact, that's not the case. The discovery of many lifeless planets across the universe, the discovery that the Earth might be unique as a place for life, would be an astonishing discovery in itself. It would be a very lonely discovery, but it would be an astonishing discovery."

More about the search for life:

• Which alien worlds are most livable?
• Maybe we are alone, after all 
• Cosmic Log archive on astrobiology

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.

Steve Helber / AP

The Antares rocket is illuminated by lights on Tuesday night, waiting for launch from a Virginia spaceport.

Orbital Sciences Corp. postponed the maiden launch of its Antares rocket on Wednesday when an umbilical data cable was disconnected prematurely from the launch vehicle's second stage.

The launch abort came at about 4:48 p.m. ET, just minutes before the Antares was due to lift off from the Mid-Atlantic Regional Spaceport on Wallops Island, Va. Orbital said the 5 p.m. ET liftoff would be rescheduled for Friday at the earliest.

"We are still examining all of the data, but it appears that the issue is fairly straightforward," Frank Culbertson, Orbital’s executive vice president and mission director for the Antares test flight, said in a company statement. "With this being the first launch of the new system from a new launch facility we have taken prudent steps to ensure a safe and successful outcome. Today, our scrub procedures were exercised and worked as planned.  We are looking forward to a successful launch on Friday."

Imagery posted to the independent NASASpaceFlight.com website showed a tower on the launch pad twisting in a motion that could have dislodged the data cord from its connector.

Orbital is giving the Antares rocket its first in-flight test in preparation for trips to the International Space Station later this year. This time around, the rocket is carrying merely a dummy payload, along with some secondary satellites that are to be deployed in orbit. But if the practice run is successful, Orbital could start providing a second line of made-in-the-USA commercial vehicles for resupplying the space station.

The Virginia-based company is following in the footsteps of California-based SpaceX, which began cargo runs to the space station last year.

Orbital and SpaceX have received hundreds of millions of dollars from NASA to develop their transports, as part of the space agency's strategy to replace the space shuttle fleet. The shuttles were retired in 2011 to make way for a new generation of spaceships capable of going beyond Earth orbit. NASA wants private companies to take over the role of getting cargo — and eventually astronauts as well — to low Earth orbit.

Orbital won NASA's contract for the Antares rocket and the Cygnus cargo capsule in 2008.

A simulated Cygnus payload is to be lofted into orbit during a 10-minute ascent, and is expected to remain in orbit for several weeks before plunging to its fiery doom in Earth's atmosphere. Four tiny satellites are to be deployed from the simulator, including three smartphone-equipped PhoneSats for NASA (Alexander, Graham, and Bell) and the commercial Dove-1 remote-sensing nanosatellite. The main point of the mission, however, is to check whether Antares is ready to send cargo to the space station.

"This is a big event for the Eastern Shore, for Wallops and for everybody in the surrounding area, but also, I think, for the country," Frank Culbertson, executive vice president and general manager of Orbital's Advanced Program Group, said during Tuesday's pre-launch briefing.

He cautioned journalists not to expect a perfect test flight. "That first word is 'test,' so if things don't go exactly as planned, we will learn what we need to learn and press on," he said.

If the test is successful, another Antares is due to send a real Cygnus capsule to the space station as early as this June. And if that demonstration flight succeeds, Orbital could proceed with a series of eight resupply flights to the station under the terms of a $1.9 billion contract with NASA. SpaceX is already two flights into its own 12-mission, $1.6 billion resupply contract.

Phil McAlister, NASA's director of commercial spaceflight development, said Orbital would play an important role in providing "assured cargo access" to the space station. The idea is that if SpaceX's Falcon 9 rocket and Dragon capsule are grounded for technical reasons, Orbital's Antares and Cygnus would serve as a backup — and vice versa. That wasn't the case during the space shuttle program, when NASA's only Plan B was to rely on other countries' spaceships.

"We are in such a better situation today, and [it's] about to be even better with the debut of this new capability," McAlister said.

NASA is following a similar approach for the development of U.S.-made spaceships for crew transport. Three companies — SpaceX, the Boeing Co. and Sierra Nevada Corp. — are splitting more than a billion dollars of NASA's money during the current phase of work. NASA expects commercial crew transports to start flying to the space station by 2017. 

Correction for 6:55 p.m. ET April 17: I've cleaned up a couple of errors, including the date when Orbital won NASA's nod in the Commercial Orbital Transportation Services program (2008, not 2007) and the SpaceX contract amount under NASA's Commercial Resupply Services program ($1.6 billion, not $1.6 million).

More about the Antares rocket:

• Five things you didn't know about Antares
• Watch as Antares rises into orbit

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.