Galaxies come in all shapes and sizes, but can generally be grouped into easily identifiable regular shapes, such as the elegant spirals or run-of-the-mill ellipticals. And then there are the irregular galaxies, which account for roughly a quarter of known galaxies, that are just kinda messy.

ANALYSIS: Galaxy Grows Monstrous X-Ray Tail

In this recent Hubble Space Telescope observation, one such irregular galaxy, located around 16 million light-years from Earth, has been observed. It looks like a loose collection of stars that have been thrown together and shuffled, like my end-of-semester university dorm room. But this galaxy, called NGC 5408, isn't just a scattering of stars, it's a whole galaxy and it's a galaxy with some interesting astronomical history.

Water ice is surprisingly abundant on Pluto's surface, a new map of the dwarf planet reveals.

Scientists created the map using data collected by NASA's New Horizons spacecraft during its epic flyby of Pluto last July.

The new map is more sensitive than an earlier version also produced using flyby observations, and thus shows more water ice — the dwarf planet's bedrock material — cropping up across Pluto's surface than had been seen previously, NASA officials said.

A new NASA organization dedicated to protecting Earth from dangerous asteroids has hit the ground running.

In early January, NASA announced the establishment of a Planetary Defense Coordination Office (PDCO), which will synchronize U.S. efforts to deal with threatening near-Earth objects (NEOs) and will supervise all NASA-funded projects to find and characterize asteroids and comets that visit Earth's neighborhood.

"There is no identified threat that we know of right now," said Lindley Johnson, NASA's new planetary defense officer. [Photos: Potentially Dangerous Asteroids in Space]

"Our job is to look for that and identify a NEO as far in advance as we can," Johnson told Space.com in an exclusive interview. "Doing so means we have the maximum amount of time to appropriately deal with the object, be it a small impactor or something that's larger, calling for a kinetic impactor mission, or whatever needs to be done."

Busy agenda

The PDCO is getting right to work. Next month, for example, the organization will conduct an open forum in Vienna, Austria, during a meeting of the United Nation's Scientific and Technical Subcommittee of the Committee on the Peaceful Uses of Outer Space (COPUOS).

That UN subcommittee has formalized the International Asteroid Warning Network (IAWN) and a Space Mission Planning Advisory Group (SMPAG) of U.N. member states that have space agencies.

"Our intent is to work within the international forums," Johnson said, "and encourage more involvement by other countries."

Johnson said that he'll also be working closely with his European Space Agency (ESA) counterparts on NEOs.

"We congratulate NASA for the establishment of their planetary defense office," said Detlef Koschny, head of the NEO Segment within the Space Situational Awareness Program Office at ESA's European Space Research and Technology Center in Noordwijk, Netherlands.

ESA is active in the field of NEOs, Koschny said, citing the NEO Coordination Centre at ESA's European Space Research Institute in Italy.

"We are fully supporting the work on defending our planet from potential asteroid impacts," Koschny told Space.com. [Photos: Asteroids in Deep Space]

NASA's European colleagues are eager to coordinate on the planetary-defense effort, Koschny's NEO Segment colleague Gerhard Drolshagen told Space.com.

"We look forward to working with the new Planetary Defense Coordination Office, building on long-standing international and inter-agency cooperation in the domain of NEO detection, risk assessment and mitigation," Drolshagen said.

NASA also recently signed a charter with the U.S. Federal Emergency Management Agency to create a Planetary Impact Emergency Response Working Group, Johnson said.

The working group will meet regularly — initially, twice a year, Johnson said — with the goal of bringing more people up to speed on the NEO hazard, and discussing how best to handle a potential impact.

Upcoming decisions

By the end of 2016, Johnson said, it should be clear whether ESA will go ahead with the proposed Asteroid Impact & Deflection Assessment mission (AIDA), and whether NASA will be a part of the project.

As it's currently envisioned, AIDA would launch two different spacecraft to the binary asteroid system Didymos: Europe's AIM probe and the Double Asteroid Redirection Test (DART) craft, which would be built by the John Hopkins University Applied Physics Laboratory in Laurel, Maryland. DART would slam into the smaller of the two asteroids in the Didymos system, and AIM would observe the results, as a way of gauging the effectiveness of this asteroid-deflection strategy.

Another decision expected this year is a go/no-go call on the Near-Earth Object Camera (NEOCam) mission, which NASA selected in September 2015 as a finalist for its next Discovery-class mission.

NEOCam would survey the regions of space closest to Earth's orbit, where potentially hazardous asteroids are most likely to be found. Among other duties, the space telescope would assess the present-day risk of NEO impacts.

NEOCam is competing with four other mission concepts for a Discovery slot (though it's also possible NASA could pick two of these ideas, officials have said). A decision will likely be announced in September 2016.

Last-chance warning system

Also this year, the second Asteroid Terrestrial-Impact Last Alert System (ATLAS) telescope is expected to be up and operating. The ATLAS project — developed by the Institute for Astronomy at the University of Hawaii — is designed to spot dangerous asteroids shortly before their final plunge to Earth. 

The first ATLAS instrument is at work on the Haleakala volcano, on the Hawaiian island of Maui. The second telescope should be operational on the Big Island's Mauna Loa this year, Johnson said.

"ATLAS is funded by NASA's NEO Observations Program, which is now integral to the Planetary Defense Coordination Office," he said. "It makes sure nothing on the small end gets through without us knowing about it … at least days to weeks before the impact."

Johnson said that he is looking forward to a good year, "finding another 1,500 to 2,000 of these objects with the current capability … and getting a higher percentage of the NEO population in our catalog."

Currently, astronomers have identified and tracked nearly 14,000 NEOs, out of a population thought to number in the millions.

Leonard David has been reporting on the space industry for more than five decades. He is former director of research for the National Commission on Space and is co-author of Buzz Aldrin's 2013 book "Mission to Mars – My Vision for Space Exploration" published by National Geographic with a new updated paperback version released in May 2015. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com.

The colossal impact that created the moon may have spawned the cosmic mashup between the rocks that ultimately became Earth and its lunar neighbor, researchers say.

Previous research suggested that about 100 million years after the solar system formed 4.6 billion years ago, the newborn Earth was hit by a Mars-size rock named Theia, named after the mother of the moon in Greek myth. Debris from the collision later coalesced into the moon.

Much remains uncertain about the precise nature of this giant impact. For instance, scientists have long debated how much debris, including water, was exchanged between the nascent Earth and moon, and whether the collision was a glancing blow or a high-energy impact. [Watch: How the Moon Was Made, and What It Did for Life]

Now scientists find evidence that the rocks that went on to become Earth and the moon were thoroughly mixed together before they separated. This suggests that "the collision that formed the moon was a high-energy impact," said study lead author Edward Young, a cosmochemist and geochemist at the University of California, Los Angeles

Moon rocks tell the tale

The researchers analyzed seven moon rock samples collected during the Apollo 12, 15 and 17 lunar missions. They also examined one lunar meteorite — a rock that a cosmic impact knocked off the moon, which later crashed on Earth.

The researchers focused on ratios between different isotopes of oxygen in the rocks. Isotopes of an element have differing numbers of neutrons from one another — for instance, oxygen-16 has eight neutrons in its nucleus, while oxygen-17 has nine. [Violent Birth of the Moon Explained (Infographic)]

The ratio of oxygen-17 to other oxygen isotopes typically gets smaller the bigger planets and moons get. This means that different planets and moons usually have distinct isotope signatures.

However, the researchers found that Earth and the moon have indistinguishable oxygen isotope ratios, within 5 parts per million when it comes to oxygen-17.

"As we continue to improve our ability to make measurements, the moon and Earth continue to be more and more alike isotopically," Young told Space.com.

Previous research from another group in Germany found subtle differences in oxygen isotope ratios between Earth and the moon, differing by about 12 parts per million when it came to oxygen-17. This prior work suggested that less mixing occurred between Earth and the moon than now proposed.

Moon-Earth mix-up

Young and his colleagues said their analysis was more precise than previous studies because they were able to identify and overcome potentially major causes of error, such as contamination by water.

"It should be remembered that the new level of precision that we are working with is challenging, and so it is not surprising that there will be some disagreement in the beginning," Young said.

Isotope geochemist Andreas Pack at the University of Göttingen in Germany, whose group previously found oxygen-isotope ratio differences between Earth and the moon, said this new research presents "high-quality data along with a sound explanation for the surprising similarity of Earth and the moon. There is nothing for me to criticize."

These findings suggest that the newborn Earth and Theia contained substantial amounts of water bearing oxygen-17, the researchers said. This water may have come in the form of ice- or water-laden minerals, they added.

In the future, "we will be measuring many more lunar samples to get a feel for what sort of variability there might be from terrain to terrain on the moon," Young said. "For example, we see evidence for oxygen isotope differences between basalts on the moon and the highlands of the moon. These differences mimic similar variability seen here on Earth."

The scientists detailed their findings in the Jan. 29 issue of the journal Science.

Follow Charles Q. Choi on Twitter @cqchoi. Follow us @Spacedotcom, Facebook and Google+. Originally posted at Space.com.