Ask An Astronaut: Mike Fossum

NASA astronaut Mike Fossum onboard the International Space Station during Expedition 28. NASA's Robonaut is also visible in the background. Image credit: NASA TV

[/caption]Following up on our successful “Ask Dr. Alan Stern” interview, we’re continuing our “Ask” series. This time, Universe Today readers will be able to Ask an Astronaut!

Here’s how it works: Readers can submit questions they would like Universe Today to ask the guest responder. Simply post your question in the comments section of this article. We’ll take the top five (or so) questions, as ranked by “likes” on the discussion posts. If you see a question you think is good, click the “like” button to give it a vote.

Keep in mind that final question acceptance is based on the discretion of Universe Today and in some cases, the responder and/or their employer.

This installment features International Space Station Expedition 29 commander, Mike Fossum.

Self-portrait of astronaut Mike Fossum taken on July 8, 2006. Image Credit: NASA / Mike Fossum
Fossum served as an Air Force test pilot until 1992, when he joined NASA. Officially selected for the Astronaut Corps in 1998, His first space flight was on July 4, 2006 as an STS-121 mission specialist.

According to NASA, Fossum completed 167 days in space as a member of the Expedition 28 and 29 crews during his third space flight. Altogether, Fossum has spent 194 days in space and performed seven spacewalks. He ranks seventh on the all-time list for cumulative spacewalking time.

Fossum and his crewmates, Expedition 29 Flight Engineers Sergei Volkov of the Russian Space Agency and Satoshi Furukawa of the Japan Aerospace Exploration Agency, returned to Earth in their Soyuz TMA-02M spacecraft at 8:26 p.m. on Nov. 21, 2011. Fossum was aboard the station during the final space shuttle mission, STS-135, which delivered supplies and equipment to the outpost. During most of his time aboard the ISS, Fossum performed science experiments and routine maintenance.

Before submitting your question, take a minute and read a bit more about Fossum at: http://www.jsc.nasa.gov/Bios/htmlbios/fossum.html

You can also read Fossum’s “Living The Dream” NASA blog at: Mike Fossum’s Blog

We’ll take questions until 6:00PM (MST) Monday, January 9th and provide a follow up article soon after with Fossum’s responses to your questions.

Dazzling Photos of the International Space Station Crossing the Moon!

Moon and International Space Station from NASA Johnson Space Center, Houston, Texas. This photo was taken in the early evening of Jan. 4. Equipment: Nikon D3S, 600mm lens and 2x converter, Heavy Duty Bogen Tripod with sandbag and a trigger cable to minimize camera shake. Camera settings: 1/1600 @ f/8, ISO 2500 on High Continuous Burst. Credit: NASA

[/caption]

Has the International Space Station (ISS) secretly joined NASA’s newly arrived GRAIL lunar twins orbiting the Moon?

No – but you might think so gazing at these dazzling new images of the Moon and the ISS snapped by a NASA photographer yesterday (Jan. 4) operating from the Johnson Space Center in Houston, Texas.

Check out this remarkable series of NASA photos above and below showing the ISS and her crew of six humans crossing the face of Earth’s Moon above the skies over Houston, Texas. And see my shot below of the Moon near Jupiter – in conjunction- taken just after the two GRAIL spacecraft achieved lunar orbit on New Year’s weekend.

In the photo above, the ISS is visible at the upper left during the early evening of Jan. 4, and almost looks like it’s in orbit around the Moon. In fact the ISS is still circling about 248 miles (391 kilometers) above Earth with the multinational Expedition 30 crew of astronauts and cosmonauts hailing from the US, Russia and Holland.

Space Station Crossing Face of Moon
This composite of images of the International Space Station flying over the Houston area show the progress of the station as it crossed the face of the moon in the early evening of Jan. 4, 2012 over NASA’s Johnson Space Center, Houston, Texas. Credit: NASA
click to enlarge

The amazing photo here is a composite image showing the ISS transiting the Moon’s near side above Houston in the evening hours of Jan 4.

The ISS is the brightest object in the night sky and easily visible to the naked eye if it’s in sight.

With a pair of binoculars, it’s even possible to see some of the stations structure like the solar panels, truss segments and modules.

Check this NASA Website for ISS viewing in your area.

How many of you have witnessed a sighting of the ISS?

It’s a very cool experience !

NASA says that some especially good and long views of the ISS lasting up to 6 minutes may be possible in the central time zone on Friday, Jan 6 – depending on the weather and your location.

And don’t forget to check out the spectacular photos of Comet Lovejoy recently shot by Expedition 30 Commander Dan Burbank aboard the ISS – through the Darth Vader like Cupola dome, and collected here

Moon and International Space Station (at lower right) on Jan 4, 2012 from NASA Johnson Space Center, Houston, Texas. Credit: NASA click to emlarge
Moon, Jupiter and 2 GRAILs on Jan. 2, 2012
Taken near Princeton, NJ after both GRAIL spacecraft achieved lunar orbit after LOI - Lunar Orbit Insertion- burns on New Year’s weekend 2012. Credit: Ken Kremer

Weekly Space Hangout for Jan. 5th, 2012

This was the first weekly space hangout, run as a Hangout on Air in Google+. On the agenda: NASA’s GRAIL Mission, the return of Phobos-Grunt, the Quadrantid meteor shower, 2012 nonsense and teleporting Obama to Mars. We were joined by Nancy Atkinson, Alan Boyle, Fraser Cain, Pamela Gay, Nicole Gugliucci, Ian O’Neill, Phil Plait, and Jon Voisey.

I apologize for the low quality of audio and video, we’re working out ways to make this all better, but I hope you enjoy the discussion.

Unlocking Cosmology With Type 1a Supernovae

New research shows that some old stars known as white dwarfs might be held up by their rapid spins, and when they slow down, they explode as Type Ia supernovae. Thousands of these "time bombs" could be scattered throughout our Galaxy. In this artist's conception, a supernova explosion is about to obliterate an orbiting Saturn-like planet. Credit: David A. Aguilar (CfA)

[/caption]Let’s face it, cosmologists catch a lot of flack. It’s easy to see why. These are people who routinely publish papers that claim to ever more finely constrain the size of the visible Universe, the rate of its breakneck expansion, and the distance to galaxies that lie closer and closer to the edges of both time and space. Many skeptics scoff at scientists who seem to draw such grand conclusions without being able to directly measure the unbelievable cosmic distances involved. Well, it turns out cosmologists are a creative bunch. Enter our star (ha, ha): the Type 1a Supernova. These stellar fireballs are one of the main tools astronomers use in order to make such fantastic discoveries about our Universe. But how exactly do they do it?

First, let’s talk physics. Type 1a supernovae result from a mismatched marriage gone wrong. When a red giant and white dwarf (or, less commonly, two white dwarfs) become trapped in a gravitational standoff, the denser dwarf star begins to accrete material from its bloated companion. Eventually the white dwarf reaches a critical mass (about 1.4 times that of our own Sun) and the natural pressure exerted by its core can no longer support its weight. A runaway nuclear reaction occurs, resulting in a cataclysmic explosion so large, it can be seen billions of light years away. Since type 1a supernovae always result from the collapse of a white dwarf, and since the white dwarf always becomes unstable at exactly the same mass, astronomers can easily work out the precise luminosity of such an event. And they have. This is great news, because it means that type 1a supernovae can be used as so-called standard candles with which to probe distances in the Universe. After all, if you know how bright something is and you know how bright it appears from where you are, you can easily figure out how far away it must be.

A Type Ia supernova occurs when a white dwarf accretes material from a companion star until it exceeds the Chandrasekhar limit and explodes. By studying these exploding stars, astronomers can measure dark energy and the expansion of the universe. CfA scientists have found a way to correct for small variations in the appearance of these supernovae, so that they become even better standard candles. The key is to sort the supernovae based on their color. Credit: NASA/CXC/M. Weiss

Now here’s where cosmology comes in. Photons naturally lose energy as they travel across the expanding Universe, so the light astronomers observe coming from type 1a supernovae will always be redshifted. The magnitude of that redshift depends on the amount of dark energy that is causing the Universe to expand. It also means that the apparent brightness of a supernova (that is, how bright it looks from Earth) can be monitored to determine how quickly it is receding from our line of view. Observations of the night sky will always be a function of a specific cosmology; but because their distances can be so easily calculated, type 1a supernovae actually allow astronomers to draw a physical map of the expansion of the Universe.

Spotting a type 1a supernova in its early, explosive throes is a rare event; after all, the Universe is a pretty big place. But when it does happen, it offers observers an unparalleled opportunity to dissect the chaos that leads to such a massive explosion. Sometimes astronomers are even lucky enough to catch one right in our cosmic backyard, a feat that occurred last August when Caltech’s Palomar Transit Factory (PTF) detected a type 1a supernova in M101, a galaxy just 25 million light years away. By the way, it isn’t just professionals that got to have all the fun! Amateur and career astronomers alike were able to use this supernova (the romantically named PTF11kly) to probe the inner workings of these precious standard candles. Want to learn more about how you can get in on the action the next time around? Check out UT’s podcast, Getting Started in Amateur Astronomy for more information.

NASA Channels “The Force” With Smart SPHERES

Three satellites fly in formation as part of the Synchronized Position Hold, Engage, Reorient, Experimental Satellites (SPHERES) investigation. Image Credit: NASA

[/caption]In an interesting case of science fiction becoming a reality, NASA has been testing their SPHERES project over the past few years. The SPHERES project (Synchronized Position Hold, Engage, Reorient, Experimental Satellites) involves spherical satellites about the size of a bowling ball. Used inside the International Space Station, the satellites are used to test autonomous rendezvous and docking maneuvers. Each individual satellite features its own power, propulsion, computers and navigational support systems.

The SPHERES project is the brainchild of David Miller (Massachusetts Institute of Technology). Miller was inspired by the floating remote “droid” that Luke Skywalker used to help hone his lightsaber skills in Star Wars. Since 2006, a set of five SPHERES satellites, built by Miller and his students have been onboard the International Space Station.

Since lightsabers are most likely prohibited onboard the ISS, what practical use have these “droids” been to space station crews?


The first SPHERES satellite was tested during Expedition 8 and Expedition 13, with a second unit delivered to the ISS by STS-121, and a third delivered by STS-116. The crew of ISS Expedition 14 tested a configuration using three of the SPHERES satellites. Since their arrival, over 25 experiments have been performed using SPHERES. Until recently, the tests used pre-programmed algorithms to perform specific functions.

“The space station is just the first step to using remotely controlled robots to support human exploration,” said Chris Moore, program executive in the Exploration Systems Mission Directorate at NASA Headquarters in Washington. “Building on our experience in controlling robots on station, one day we’ll be able to apply what we’ve learned and have humans and robots working together everywhere from Earth orbit, to the Moon, asteroids, and Mars.”

International Space Station researcher Mike Fossum, commander of Expedition 29, puts one of the Smart SPHERES through its paces. Image Credit: NASA
In November, the SPHERES satellites were upgraded with “off-the-shelf” smartphones by using an “expansion port” Miller’s team designed into each satellite.

“Because the SPHERES were originally designed for a different purpose, they need some upgrades to become remotely operated robots,” said DW Wheeler, lead engineer in the Intelligent Robotics Group at Ames.

Wheeler added, “By connecting a smartphone, we can immediately make SPHERES more intelligent. With the smartphone, the SPHERES will have a built-in camera to take pictures and video, sensors to help conduct inspections, a powerful computing unit to make calculations, and a Wi-Fi connection that we will use to transfer data in real-time to the space station and mission control.”

In order to make the smartphones safer to use onboard the station, the cellular communications chips were removed, and the lithium-ion battery was replaced with AA alkaline batteries.

By testing the SPHERES satellites, NASA can demonstrate how the smart SPHERES can operate as remotely operated assistants for astronauts in space. NASA plans additional tests in which the compact assistants will perform interior station surveys and inspections, along with capturing images and video using the smartphone camera. Additional goals for the mission include the simulation of free-flight excursions, and possibly other, more challenging tasks.

“The tests that we are conducting with Smart SPHERES will help NASA make better use of robots as assistants to and versatile support for human explorers — in Earth orbit or on long missions to other worlds and new destinations,” said Terry Fong, project manager of the Human Exploration Telerobotics project and Director of the Intelligent Robotics Group at NASA’s Ames Research Center in Moffett Field, Calif.

You can view a video of the SPHERES satellites in action at: http://ti.arc.nasa.gov/m/groups/intelligent-robotics/smartspheres_test_2011-11-01-4x.avi (Sorry, no lightsaber action.).

If you’d like to learn more about NASA’s SPHERES program, visit: http://www.nasa.gov/mission_pages/station/research/experiments/SPHERES.html

Source: NASA Telerobotics News

Four New Exoplanets to Start Off the New Year!

Artist's conception of a gas giant orbiting close to its star. Credit: NASA/JPL-Caltech/T. Pyle (SSC)

[/caption]

It’s only a few days into 2012 and already some new exoplanet discoveries have been announced. As 2011 ended, there were a total of 716 confirmed exoplanets and 2,326 planetary candidates, found by both orbiting space telescopes like Kepler and ground-based observatories. The pace of new discoveries has accelerated enormously in the past few years. Now there are four more confirmed exoplanets to add to the list.

The four planets, HAT-P-34b, HAT-P-35b, HAT-P-36b, HAT-P-37b all have very tight orbits around their (four different) stars, taking only 5.5, 3.6, 1.3 and 2.8 days to complete an orbit. Compare that to Mercury, which takes 87.969 days and 365 days of course for Earth.

They were found by astronomers with the Harvard-Smithsonian Center for Astrophysics which operates a network of ground-based telescopes known as the HATNet project. The first exoplanet discovery by HATNet, the planet HAT-P-1b, was in 2006.

They are all “hot jupiter” type planets, gas giants which orbit very close to their stars and so are much hotter than Earth, like Mercury in our own solar system. Mercury though, of course, is a small rocky world, but in some alien solar systems, gas giants have been found orbiting just as close to their stars, or even closer, than Mercury does here. HAT-P-34b however, may have an “outer component” and is in a very elongated orbit. The other three are more typical hot Jupiters. They were discovered using the transit method, when a planet is aligned in its orbit so that it passes in front of its star, from our viewpoint.

So what does this mean? If exoplanet discoveries continue to grow exponentially as expected, then 2012 should be a good year, not only for yet more new planets being found, but also for our understanding of these alien worlds and how such a wide variety of solar systems came to be. We’ve come a long way from 1992 and the first exoplanet discoveries and things promise to only get more exciting in the future.

If you want to get your exoplanet news quickly this year, I recommend the Exoplanet App for iPhone, iPad and iPod Touch. You can also follow @ExoplanetApp on Twitter.

The abstract and paper are here.

Suburu Telescope Captures Hidden Planets In Stellar Dust Ring

Near-infrared (1.6 micron) image of the debris ring around the star HR 4796 A. An astronomical unit (AU) is a unit of length that corresponds to the average distance between the Earth and Sun, almost 92 million miles (over 149 million km). The ring consists of dust grains in a wide orbit (roughly twice the size of Pluto's orbit) around the central star. Its edge is so precisely revealed that the researchers could confirm a previously suspected offset between the ring's center and the star's location. This "wobble" in the dust's orbit is most likely caused by the unbalancing action of – so far undetected – massive planets likely to be orbiting within the ring. Furthermore, the image of the ring appears to be smudged out at its tips and reveals the presence of finer dust extending out beyond the main body of the ring. Credit: Suburu

[/caption]

No. It’s not a new atomic image – it’s a very unusual look at a star which could help further our understanding of stellar disk structure and planetary formation. As part of the SEEDS (Strategic Exploration of Exoplanets and Disks with Subaru Telescope/HiCIAO) project, this image of star HR 4796 was taken with Subaru’s planet-finder camera, HiCIAO (High Contrast Instrument for the Subaru Next Generation Adaptive Optics). At only about 8-10 million years old, the feature of this stellar image is only about 240 light years away from Earth, yet fully displays its ring of dust grains which reach out about twice the distance as Pluto’s orbit from the central star. This image produced by an international group led by Motohide Tamura of NAOJ (National Astronomical Observatory of Japan) is so wonderfully detailed that an offset between its center and the star’s position can be measured. While the offset was predicted by data from the Hubble and another research group, this new photographic evidence not only confirms its presence – but shows it to be larger than expected.

With new data to work from, researchers began to wonder exactly what could have caused the dust torus to run off its axis. The easiest explanation would be gravitational force – where one or more planets located inside the gap within the ring could possibly be affecting the disk. This type of action could account for an “unbalancing” which could act in a predictable manner. Current computer modeling has shown these types of “gravitational tides” can mold a dust torus in unusual ways and they cite similar data gathered from observations of bright star, Formalhaut. Since no planet candidates have yet been directly observed around HR 4796, chances are any planets present are simply too small and dim to be spotted. However, thanks to the new Suburu image, researchers feel confident their presence could be the source of the circumstellar dust ring wobble.

With image accuracy as pinpoint as the Hubble Space Telescope, the Suburu near-infrared depiction allows for extremely accurate measurements by employing its adaptive optics system. This type of advanced astrophotography also allows for angular differential imaging – by-passing the glare of the central star and enhancing the faint signature of the dust ring. Such techniques are able to establish heightened information about the relationship of the circumstellar disk and gelling planets… a process which may begin from the “left-overs” of initial star formation. As surmised, this material could either be picked up by newly formed planets or be pushed out the system via stellar winds. Either way, it is a process which eliminates the majority of the dust within a few tens of millions of years. However, there are a few stars which continue to hold on to a “secondary disk” – a collection of dust which could be attributed to the collision of planetesimals. In the case of HR 4796, this is a likely scenario and studying it may provide a better understanding of how planets could form in this alternate debris disk.

Original Story Source: Suburu Telescope News Release. For Further Reading: Direct Images of Disks Unravel Mystery of Planet Formation.

Missions that Weren’t: One-Way Mission to the Moon

The Apollo lunar landing module as it looked in 1963. Image credit: wired.com

[/caption]

When President Kennedy promised America a lunar landing in 1961, he effectively set the Moon as the finish line in the space race. In the wake of his speech, NASA began scrambling to find a way to reach the Moon in advance of the Soviet Union, which at the time held a commanding lead in space. Apollo, already on the drawing board as an Earth orbiting program, was revised to reflect the lunar goal and Gemini was established as the interim program.

The pieces were in place; all NASA needed was a way to get to the Moon. Against this pressing background, two men proposed a desperate and direct mission to get an American on the Moon as quickly as possible. 

A schematic showing three different flight modes for Apollo lunar missions. Image credit: NASA

The proposal came from two Bell Aerosystems Company employees. John M. Cord was a Project Engineer in the Advanced Design Division and Leonard M. Seale was a psychologist in charge of the Human Factors Division. At the Institute of Aerospace Sciences in Los Angeles in 1962, the pair unveiled their “One-Way Manned Space Mission” proposal.

The plan called for a one-man spacecraft to follow a direct ascent path to the Moon. Ten feet wide and seven feet tall, the empty spacecraft weighed less than half the much smaller Mercury capsule. Inside, the astronaut would have enough water for 12 days, oxygen for 18 with a 12-day emergency reserve, a battery-powered suit and backpack, and all the tools and medical supplies he might need.

He would land on the Moon after a two-and-a-half day trip and have just under ten days to set up his habitat. As part of his payload, the astronaut would arrive with four cargo modules with pre-installed life support systems and a nuclear reactor to generate electrical power. Two mated modules would become his primary living quarters, while the others placed in caves or buried in rubble — a feature Cord and Seale assumed would dominate the lunar landscape — would provide a shelter from solar storms.

A possible configuration for a direct ascent Apollo spacecraft. Image credit: NASA

With his temporary home set up, he would wait a little over two years for another mission to come and collect him. Cord and Seale estimated that this mission could be launched as early as 1965, a year of expected minimal solar activity. Larger launch vehicles capable of sending the three-man Apollo spacecraft would be ready by 1967. The one-way spaceman would have a long but finite stay on the Moon.

This proposal was incredibly practical. Since the astronaut wouldn’t be launching from the lunar surface, he wouldn’t need to carry the necessary propellant. Since he would return to Earth in another spacecraft, his own spacecraft wouldn’t need a heavy heat shield or parachutes. The one-way mission was a light and efficient proposal.

But it was also dangerous. The proposal didn’t include any redundancies; the direct ascent path gave the astronaut no chance to abort his mission after launch. He would have to deal with any problems that arose knowing he wouldn’t be able to make a quick return home.

Luckily for the possible astronaut the proposal was never seriously considered. In July 1962, a few weeks after the one-way mission was proposed, NASA announced its selection of the more complicated but safer Lunar Orbit Rendezvous (LOR) mode for Apollo missions.

John Houbolt explains the benefits of Lunar Orbit Rendezvous over Direct Ascent. Image credit: NASA/courtesy of nasaimages.org

New Research Casts Doubt on the Late Heavy Bombardment

Map of the Serenitatis basin area of the Moon
Click on the image to download the full map and explore it in more detail.

[/caption]

Was the early solar system bombarded with lots of big impacts? This is a question that has puzzled scientists for over 35 years. And it’s not just an academic one. We know from rocks on Earth that life began to evolve very early on, at least 3.8 billion years ago. If the Earth was being pummeled by large impacts at this time, this would certainly have affected the evolution of life. So, did the solar system go through what is known as the Late Heavy Bombardment (LHB)? Exciting new research, using data from the Lunar Reconnaissance Orbiter Camera (LROC) may cast some doubt on the popular LHB theory.

It’s actually quite a heated debate, one that has polarized the science community for quite some time. In one camp are those that believe the solar system experienced a cataclysm of large impacts about 3.8 billion years ago. In the other camp are those that think such impacts were spread more evenly over the time of the early solar system from approximately 4.3 to 3.8 billion years ago.

The controversy revolves around two large impact basins, which are found fairly close to each other on the Moon. The Imbrium basin is one of the youngest basins on the near side of the Moon, while the Serenetatis basin is thought to be one of the oldest. Both are flooded with volcanic basalts and are big enough to be seen from Earth with the naked eye.


Map of the Serenitatis basin area of the Moon

What if the Apollo 17 samples didn't come from the Serenitatis basin, where the astronauts collected them, but rather from the Imbrium basin, located some 600 km away? Studies from the new Lunar Reconnaissance Orbiter Camera suggest this may be the case. If true, this means Serenitatis is much older than the Imbrium basin and a solar system-wide impact catastrophe is not needed to explain the uncannily close ages of the Imbrium and Serenitatis basins.

Image credit: NASA
 Click on the image to download the full map and explore it in more detail.

Scientists know the relative ages of such lunar basins because of a concept called superposition. Basically, superposition states that what is on top must be younger than what is beneath. Using such relationships, scientists can determine which basins are older and which are younger.

To get an absolute age, though, scientists need actual bits of rock, so they can use radiometric dating techniques. The lunar samples returned by the Apollo program provided exactly that.  But, the Apollo samples suggest that the Imbrium and Serenitatis basins are barely 50 million years apart.

Relative age dating tells us there are over 30 other basins that formed within that time frame.  This means that roughly one major impact occurred every 1.5 million years! Now, 1.5 million years may sound like a long time. But consider the last large impact that happened on Earth, the Chicxulub event 65 million years ago, which is thought to have exterminated the dinosaurs. Imagine another 40 dinosaur-killing impacts occurring since then. It would be surprising if any life survived such a barrage!

This is why a team of researchers, led by Dr. Paul Spudis of the Lunar and Planetary Institute, is looking very carefully at this question. Their research is using the principle of superposition to show that several of the areas visited by the Apollo program were blanketed by material from the Imbrium impact. This could mean that many of the collected Apollo materials may be sampling the same event.

Dr. Spudis’s research focuses on the Montes Taurus area, between the Serenitatis and Crisium basins, not far from the Apollo 17 landing site. This is a region dominated by sculpted hills that have been interpreted to be ejected material from the adjacent Serenitatis basin impact. But, Dr. Spudis and his team have found that, instead, this sculpted material comes from the Imbrium basin some 600 kilometers away.

Previous data of this area, from the Lunar Orbiter IV camera, hadn’t shown this because a fog on the camera lens made the details difficult to see (this fog problem was eventually resolved, and Lunar Orbiter IV provided a lot of useful data on other parts of the Moon).The new LROC data, however, shows that the sculpted terrain seen at Apollo 17 is very widespread, extending far beyond the Montes Taurus region. Furthermore, the grooves and lineated features of this terrain point to the Imbrium basin, not the Serenitatis basin, and line up with similar features in the Alpes and Fra Mauro Formations, which are known to be ejecta from the Imbrium impact. In the north of Serenitatis, these Imbrium formations even seem to transform into the Montes Taurus, confirming that the sculpted hills do, in fact, originate from the Imbrium impact.

LROC Data of Serenitatis basin area on the Moon
Recent high quality data from the Lunar Reconnaissance Orbiter Camera shows that the sculpted terrain, which is present at the Apollo 17 landing site, is related to material that is known to be from the Imbruim impact. This means that Apollo 17 may have sampled Imbrium and not Serenitatis material. This could explain the unusually close ages of these two basins, suggested by the Apollo samples. If so, the Serenitatis impact may have occurred much earlier than previously thought, meaning that a barrage of frequent bombardments did not occur, and life on Earth could have evolved without being molested by too many impact events.

Image credit: NASA/GSFC/Arizona State University
 Click on the image to explore the LROC data in greater detail.

If the sculpted hills are Imbruim ejecta, then it is possible that Apollo 17 sampled Imbrium and not Serenitatis materials.  That casts suspicion on the very close radiometric ages of these two basins. Perhaps these ages are so close because we effectively measured the same material. In that case, the age of Serenitatis could be much older than the 3.87 billion years the Apollo 17 samples suggest.  If true, this would mean that there was no Late Heavy Bombardment at the time life was forming on the early Earth, leaving life to evolve with relatively few impact-related interruptions.

Source:
Spudis et al., 2011, Journal of Geophysical Research, V116, E00H03