CNET points out the far side of the moon — the one that never faces earth — is "rugged, spotted with tons of craters" and "filled with totally different elements."

"In essence, our moon has two faces, and scientists are still trying to solve the mystery of why they're so different." But a paper published Friday in the journal Science Advances might finally have an explanation for one major aspect of this enigmatic lunar duality. It has to do dark shadows, a massive impact many billions of years ago, and... lava....

They used computer simulations to see what might've gone on long, long (long) ago, way before there was any volcanic activity on the moon's surface. More specifically, they re-created a massive impact that, billions of years ago, changed the base of the moon, forming a gigantic crater that we now refer to as the South Pole-Aitken (SPA) basin.... What they found is that this huge smash would've created a plume of heat that carried a bunch of specific chemical elements to the near side of the moon, and not the far side. "We expect that this contributed to the mantle melting that produced the lava flows we see on the surface," Jones said.

In other words, those elements presumably contributed to an era of volcanism on the lunar face we can see from Earth but it left the far side untouched.

Ars Technica looks at the "in-space propulsion company" Impulse Space, which just announced $20 million in seed funding this week to help it build something called an "orbital transfer vehicle."

The company was founded by rocket scientist Tom Mueller, who the article describes as the first employee hired by Elon Musk for SpaceX, leading the development of SpaceX's Merlin rocket engine.

Impulse Space is apparently positioning itself for its own role in a future with lots of reusable rockets and cheaper launch costs: Founded last September, Impulse Space will initially seek to provide "last mile" delivery services for satellites launched as part of rideshare missions, likely including on SpaceX's workhorse Falcon 9 rocket.... While the company is not ready to discuss its specific technology, the goal is to deliver the most delta-V capability [velocity from fuel-burning] in the most efficient manner.

Impulse Space released a teaser video on this earlier this month. [The video's title? "Hello, Solar System...!" And it concludes with the words "Big things have small beginings."]

Impulse Space will seek to complement launch services with sustainable delivery in space, using green propellants and having vehicles with de-orbit capability. Barry Matsumori, who recently joined as the company's chief operating officer, said the company recognizes that if tens or hundreds of satellites will be launching on these heavy-lift rockets, they're going to need to reach different orbits and have different purposes... The company's initial business strategy involves low Earth orbit, but it envisions the need for sustainable transportation from the Earth to the Moon — in the form of a tug — and the storage and movement of propellant in both low Earth orbit and the lunar environment.

Once a company mines a space resource, after all, it will have to go somewhere.

SpaceX has ended production of new Crew Dragon astronaut capsules, a company executive told Reuters, as Elon Musk's space transportation company heaps resources on its next-generation spaceship program. From the report: Capping the fleet at four Crew Dragons adds more urgency to the development of the astronaut capsule's eventual successor, Starship, SpaceX's moon and Mars rocket. Starship's debut launch has been delayed for months by engine development hurdles and regulatory reviews. It also poses new challenges as the company learns how to maintain a fleet and quickly fix unexpected problems without holding up a busy schedule of astronaut missions.

"We are finishing our final (capsule), but we still are manufacturing components, because we'll be refurbishing," SpaceX President Gwynne Shotwell told Reuters, confirming the plan to end Crew Dragon manufacturing. She added that SpaceX would retain the capability to build more capsules if a need arises in the future, but contended that "fleet management is key." Musk's business model is underpinned by reusable spacecraft, so it was inevitable the company would cease production at some point. But the timing was not known, nor was his strategy of using the existing fleet for its full backlog of missions. "Crew Dragon has flown five crews of government and private astronauts to space since 2020, when it flew its first pair of NASA astronauts and became the U.S. space agency's primary ride for getting humans to and from the International Space Station," notes Reuters.

NASA plans to encourage the development of another commercial vehicle that can land its Artemis astronauts on the moon. Space.com reports: In April 2021, NASA picked SpaceX to build the first crewed lunar lander for the agency's Artemis program, which is working to put astronauts on the moon in the mid-2020s and establish a sustainable human presence on and around Earth's nearest neighbor by the end of the decade. But SpaceX apparently won't have the moon-landing market cornered: NASA announced today (March 23) that it plans to support the development of a second privately built crewed lunar lander.

"This strategy expedites progress toward a long-term, sustaining lander capability as early as the 2026 or 2027 timeframe," Lisa Watson-Morgan, program manager for the Human Landing System Program at NASA's Marshall Space Flight Center in Alabama, said in a statement today. "We expect to have two companies safely carry astronauts in their landers to the surface of the moon under NASA's guidance before we ask for services, which could result in multiple experienced providers in the market," Watson-Morgan added. [...] Congress is "committed to ensuring that we have more than one lander to choose [from] for future missions," [NASA Administrator Bill Nelson] said during a news conference today, citing conversations he's had with people on Capitol Hill over the past year. "We're expecting to have both Congress support and that of the Biden administration," Nelson said. "And we're expecting to get this competition started in the fiscal year [20]23 budget."

Exact funding amounts and other details should be coming next week when the White House releases its 2023 federal budget request, he added. "So what we're doing today is a bit of a preview," Nelson said. "I think you'll find it's an indication that there are good things to come for this agency and, if we're right, good things to come for all of humanity." NASA plans to release a draft request for proposals (RFP) for the second moon lander by the end of the month and a final RFP later this spring, agency officials said. If all goes according to plan, NASA will pick the builder of the new vehicle in early 2023. That craft will have the ability to dock with Gateway, the small moon-orbiting space station that NASA plans to build, and take people and scientific gear from there to the surface (and back). This newly announced competition will be open to all American companies except SpaceX. But Elon Musk's company will have the opportunity to negotiate the terms of its existing contract to perform additional lunar development work, NASA officials said during today's news conference.

sciencehabit shares a report from Science.org: For years, scientists have believed frigid craters at the Moon's poles hold water ice, which would be both a scientific boon and a potential resource for human missions. Now, researchers have discovered (PDF) a reason why the ice has persisted on an otherwise bone-dry world: Some polar craters may be protected by ancient magnetic fields. Researchers have known about the anomalies ever since the Apollo 15 and 16 missions in 1971 and 1972, when astronauts measured regions of unusual magnetic strength on the surface. Some anomalies are now known to be up to hundreds of kilometers across. Although their origin is debated, one possibility is they were created more than 4 billion years ago when the Moon had a magnetic field and iron-rich asteroids crashed into its surface. The resultant molten material may have been permanently magnetized.

Thousands of the anomalies are thought to exist across the lunar surface, but the team mapped ones at the south pole in detail using data from Japan's Kaguya spacecraft, which orbited the Moon from 2007 to 2009. They found at least two permanently shadowed craters that were overlapped by these anomalies, the Sverdrup and Shoemaker craters, and there are likely more. Although the remnant fields are thousands of times weaker than Earth's, they could be sufficient to deflect the solar wind. Craters with known anomalies could become prime targets for science and exploration. NASA is already planning to visit the south polar region with a rover due for launch next year, called VIPER, and the agency intends to send humans there later this decade as part of its Artemis program. Studying the ice could reveal how it was delivered, which may in turn shed light on how Earth got its water.

This week Silicon Valley's Computer History Museum posted a PDF transcript (and video excerpts) from an interview with 81-year-old Margaret Hamilton, the programmer/systems designer who in the 1960s became director of the Software Engineering Division at the MIT Instrumentation Laboratory which developed the on-board flight software for NASA's Apollo program. Prior to that Hamilton had worked on software to detect an airplane's radar signature, but thought, "You know, 'I guess I should delay graduate school again because I'd like to work on this program that puts all these men on the Moon....'"

"There was always one thing that stood out in my mind, being in the onboard flight software, was that it was 'man rated,' meaning if it didn't work a person's life was at stake if not over. That was always uppermost in my mind and probably many others as well."

Interestingly, Hamilton had originally received two job offers from the Apollo Space Program, and had told them to flip a coin to settle it. ("The other job had to do with support systems. It was software, but it wasn't the onboard flight software.") But what's fascinating is the interview's glimpses at some of the earliest days of the programming profession: There was all these engineers, okay? Hardware engineers, aeronautical engineers and all this, a lot of them out of MIT... But the whole idea of software and programming...? Dick Battin, Dr. Battin, when they told him that they were going to be responsible for the software...he went home to his wife and said he was going to be in charge of software and he thought it was some soft clothing...
Hamilton also remembers in college taking a summer job as a student actuary at Travelers Insurance in the mid-1950s, and "all of a sudden one day word was going around Travelers that there were these new things out there called computers that were going to take away all of their jobs... Pretty soon they wouldn't have jobs. And so everybody was talking about it. They were scared they wouldn't have a way to make a living.

"But, of course, it ended up being more jobs were created with the computers than there were...."

Hamilton's story about Apollo 8 is amazing...

Right now an asteroid is zooming past earth "at a relatively close distance" reports Newsweek, "and the event can be viewed live." The asteroid, called 2022 ES3, will be traveling at 41,000 miles per hour when it comes between the moon and the Earth at around 2:18 p.m. ET on Sunday, March 13, according to NASA's Center for Near Earth Object Studies (CNEOS).

The space rock isn't expected to hit Earth. Instead, it will pass by at a distance of about 206,000 miles, which is about 87 percent of the distance between us and the moon.

The event provides a great viewing opportunity. An Italian astronomy organization called the Virtual Telescope Project, which often tracks asteroids and other space objects through the sky, is due to host a livestream of what it calls 2022 ES3's "very close, but safe, encounter with us" on its WebTV page starting at 18:30 UTC on March 13th.

Astronomers don't consider 2022 ES3 to be potentially hazardous, probably due to its size. The asteroid is predicted to be somewhere between 33 and 72 feet in diameter — about as wide as the length of a bowling lane.... [S]cientists track more than 28,000 near-Earth asteroids as they travel through the solar system. Around 900 of these are more than one kilometer, or 3,280 feet, in size.

"The European Space Agency has announced it has chosen a team to make oxygen on the moon," reports Digital Trends.

"The team, led by aerospace manufacturer Thales Alenia Space, will design and build a payload to create oxygen from lunar soil." [C]arrying oxygen into space using rockets is inefficient, so it would be better if astronauts could find ways to make what they need in the places they are exploring. This principle is called in-situ resource utilization and is a key idea for future missions to the moon and Mars.

The payload for the moon will be designed to create between 50 and 100 grams of oxygen from the dusty material which covers the moon, called regolith. The aim is to extract 70% of the available oxygen in the sample within a 10 day period. That time limit is because it will need to operate within the window of available solar power in a lunar day, which is around two weeks long.

Previous experiments and concepts have shown that it is possible to extract oxygen from lunar regolith, which is made up of around 40 — 45% oxygen by weight. Now, the challenge is to make a workable system within the constraints of size and materials.
A systems engineer from the space agency's design facility has high hopes for the project, according to a statement released Wednesday. "Being able to extract oxygen from moonrock, along with useable metals, will be a game-changer for lunar exploration, allowing the international explorers set to return to the Moon to 'live off the land' without being dependent on long and expensive terrestrial supply lines."

Scientists at NASA's Johnson Space Center in Houston are preparing to open the first tube that one of the astronauts on the Apollo missions hammered into the surface of the moon. As NPR reports, it's "remained tightly sealed all these years since that 1972 Apollo 17 mission -- the last time humans set foot on the moon." From the report: The unsealed tube from that mission was opened in 2019. The layers of lunar soil had been preserved, and the sample offered insight into subjects like landslides in airless places. Because the sample being opened now has been sealed, it may contain something in addition to rocks and soil: gas. The tube could contain substances known as volatiles, which evaporate at normal temperatures, such as water ice and carbon dioxide. The materials at the bottom of the tube were extremely cold at the time they were collected. The amount of these gases in the sample is expected to be very low, so scientists are using a special device called a manifold, designed by a team at Washington University in St. Louis, to extract and collect the gas.

Another tool was developed at the European Space Agency (ESA) to pierce the sample and capture the gases as they escape. Scientists there have called that tool the "Apollo can opener." The careful process of opening and capturing has begun, and so far, so good: the seal on the inner sample tube seems to be intact. Now, the piercing process is underway, with that special "can opener" ready to trap whatever gases might come out. If there are gases in the sample, scientists will be able to use modern mass spectrometry technology to identify them. (Mass spectrometry is a tool for analyzing and measuring molecules.) The gas could also be divided into tiny samples for other researchers to study.

If Congress' sweeping new spending bill is signed, it would finally provide full funding to some major NASA projects that have been underfunded over the last few years. From a report: Notably, NASA's program to develop a new human lunar lander would be fully funded as the president's budget requested, as will a program to develop new commercial space stations in low Earth orbit. Overall, NASA would receive $24.041 billion for 2022 in this new bill, which will fund the US government for fiscal year 2022. NASA's portion is roughly $800 million less than the $24.8 billion that President Joe Biden's budget request called for in May of 2021. However, NASA would still see a slight bump from its total funding for fiscal year 2021, which sat at $23.27 billion.

Though Congress's plan would not fully meet the president's budget request, there are a few projects that House and Senate lawmakers are finally agreeing to fund in their entirety. The bill would give NASA's human landing system the full $1.195 billion that the request asked for. Currently, NASA is developing a new human lunar lander as part of its Artemis program, an initiative to send the first woman and first person of color to the Moon. Previously, Congress showed its reluctance to give NASA the money it requested for the lander. For 2021, appropriators only provided $850 million of the requested $3.4 billion for the lander.

After years of zooming through deep space, a presumed leftover piece of a Chinese rocket slammed into the Moon today, just as space tracking experts expected it would. From a report: At least, it should have hit the Moon around 7:30AM ET this morning, as long as the law of gravity has not changed. The collision brings an end to the rocket's life in space and likely leaves a fresh new crater on the Moon that may be up to 65 feet wide. The now-expired rocket has caused quite a buzz this past month. First of all, the vehicle was never intended to crash into the Moon, making it a rare piece of space debris to find its way to the lunar surface by accident. Additionally, there was some confusion over its identity, with various groups trying to nail down exactly where the rocket came from.

Originally, space trackers thought it was a leftover piece of a SpaceX Falcon 9 rocket that had launched a weather satellite back in 2015. But after careful analysis, various groups of space trackers confirmed that the rocket was likely leftover from the launch of China's Chang'e 5-T1 mission -- a flight that launched in 2014 to test out technology needed to bring samples back from the Moon. That mission, launched on a Chinese Long March 3C rocket, sent a spacecraft looping around the Moon in an attempt to see if China could send a vehicle to the Moon and then bring it back to Earth. Given the flight profile of the Chang'e 5-T1 mission and the tracking of the mystery object, astronomers are fairly certain that a chunk of the Long March 3C rocket has remained in an extremely elongated orbit around Earth ever since, only to find its way to the far side of the Moon.

An anonymous reader quotes a report from Ars Technica: This week, the US Air Force Research Laboratory released a video on YouTube that didn't get much attention. But it made an announcement that is fairly significant -- the US military plans to extend its space awareness capabilities beyond geostationary orbit, all the way to the Moon. "Until now, the United States space mission extended 22,000 miles above Earth," a narrator says in the video. "That was then, this is now. The Air Force Research Laboratory is extending that range by 10 times and the operations area of the United States by 1,000 times, taking our reach to the far side of the Moon into cislunar space."

The US military had previously talked about extending its operational domain, but now it is taking action. It plans to launch a satellite, likely equipped with a powerful telescope, into cislunar space. According to the video, the satellite will be called the Cislunar Highway Patrol System or, you guessed it, CHPS. The research laboratory plans to issue a "request for prototype proposals" for the CHPS satellite on March 21 and announce the contract award in July. The CHPS program will be managed by Michael Lopez, from the lab's Space Vehicles Directorate. (Alas, we were rooting for Erik Estrada).

This effort will include the participation of several military organizations, and it can be a little confusing to keep track of. Essentially, though, the Air Force lab will oversee the development of the satellite. The US Space Force will then procure this capability for use by the US Space Command, which is responsible for military operations in outer space. Effectively, this satellite is the beginning of an extension of operations by US Space Command from geostationary space to beyond the Moon. [...] So why is US Space Command interested in expanding its theater of operations to include the Moon? The primary reason cited in the video is managing increasing space traffic in the lunar environment, including several NASA-sponsored commercial missions, the space agency's Artemis program, and those of other nations. Another strategic element includes the ability to detect space objects, such as those placed into cislunar space by other governments, that could swing around the Moon and potentially come back to attack a U.S. military satellite in geostationary space.

"I think that's far fetched, but it is feasible from a physics perspective and would definitely exploit a gap in their current space domain awareness," said Brian Weeden, director of program planning for the Secure World Foundation. "I think they are far more concerned about that than any actual threats in cislunar space because the US doesn't have any military assets in cislunar space right now."

Slashdot reader Tangential shares what he describes as "an interesting article on Gizmodo discussing how we could easily contaminate other planets/moons as we explore them."

"Based on our recently demonstrated vulnerability to locally evolved bacteria and viruses, what will other worlds's pathogens do to us (and what will ours do to them?) What I also find interesting is what a small percentage of SciFi actually addresses this."

From Gizmodo's article: The year is 2034. Humans have sent a probe to Jupiter's moon Europa to drill through the icy surface and photograph the ocean beneath. In the few hours before it stops functioning, the probe returns images of shapes that could be some form of life. Scientists quickly organize a followup mission that will collect samples of that spot and bring them back to Earth. But, unknown to anyone, the first probe wasn't sterile — it carried a hardy bacteria that had survived even the mission's clean rooms. By the time the samples finally reach Earth years later, they're dominated by this bacteria, which has happily set up shop in Europa's dark, salty waters. Just like that, our first opportunity to study a truly alien ecosystem has been destroyed.

This is a nightmare scenario for NASA and other space agencies, and it's one they've worked intensely to avoid with every mission to another orb. But some researchers from a lesser-known branch of ecology argue that even the current strict standards aren't rigorous enough, and as more ambitious missions to other planets and moons get ready to launch, the risk of interplanetary contamination becomes more dire. They say we need to better plan for "forward contamination," in which our technology disseminates Earth microbes, as well as "back contamination," in which life from elsewhere hitches a ride to Earth.

In fact, we already have a playbook to lean on: the discipline of invasion science, the study of how species on our planet invade each other's ecosystems. "What I would say is that, given that there are now concrete plans in place to explore new areas that could have extant life — these pose a new set of risks that were not in play before," Anthony Ricciardi, a professor of invasion ecology and aquatic ecosystems at McGill University, told Gizmodo. "Invasion science has been applied to biosecurity at national and international levels. My colleagues and I believe that it could similarly guide biosecurity at the planetary or interplanetary scales."

Because of the groundbreaking technological advances of recent years, our ability to explore other worlds — from asteroids to planets to ocean moons — is expanding, and so are the risks that come with that. NASA plans to bring bits of Mars to Earth in the early 2030s, and missions to Titan and Europa, which could very well host life, are set to launch this decade.... Although the 2034 Europa tale is invented, there's plenty of precedent for it. We've likely accidentally brought drug-resistant bacteria into the Antarctic ecosystem already, infecting seabirds and seals.

Our lack of foresight and carelessness is driving mass extinctions on Earth — are we willing to do the same thing to the next inhabited world we touch?

While billionaires are battling it out in a race to colonise the moon, mere stratospherically rich mortals on Earth were able to grab a small slice of space rock for themselves on Wednesday at Christie's annual sale of rare and unusual meteorites. From a report: Star-gazers and meteorite enthusiasts bid frantically for fragments of the "oldest matter humankind can touch" -- as the auction house put it -- while other objects such as a comet-cracked kennel from Costa Rica sold for tens of thousands of dollars. A 15g fragment of the Winchcombe meteorite, which briefly became Britain's most coveted rock after the bright fireball was seen blazing across the sky over the Cotswold town last year, sold for $30,200, while a smaller 1.7g fragment fetched $12,600.

According to the Christie's catalogue of the 66-lot Deep Impact: Martian, Lunar and other Rare Meteorites" sale, only 602g of Winchcombe was ever found -- with 90% of the material now housed in the UK's national collection, curated by London's Natural History Museum. Among the more usual items for sale was a dog house hit by a meteorite which crashed through the tin roof in April 2019 in Aguas Zarcas, Costa Rica. But while it was expected to sell for as much as $300,000, after all it boasted a seven-inch hole which "marks where the meteorite punctured the roof," it finally sold for $44,100.

A distant white dwarf is surrounded by space rocks marching in perfect time. This observation offers hints of what may be the first planet we have detected in the habitable zone of one of these stellar corpses, suggesting that they might be just as good for life as bigger, younger stars. From a report: "A lot of people think of a white dwarf as a dead system or a dead end, but this tells us that there is a lot of stuff going on around white dwarfs," says Jay Farihi at University College London. He and his colleagues spotted these hints while observing a star called WD 1054-226, which lies about 118 light years away, using several powerful telescopes. They found that something appeared to be regularly passing in front of the star, causing dips in its light. The biggest dip happened every 23.1 minutes, in a pattern that repeated every 25 hours.The measurements indicate, the report says, that the star is surrounded by a ring of 65 comet-sized or moon-sized objects, remarkably evenly spaced in their orbits.

schwit1 shares a report from Politico: Starship is threatening NASA's moon contractors, which are watching its progress with a mix of awe and horror. "They are shitting the bed," said a top Washington space lobbyist who works for SpaceX's competitors and asked for anonymity to avoid upsetting his clients. NASA and its major industry partners are simultaneously scrambling to complete their own moon vehicles: the Space Launch System mega-rocket and companion Orion capsule. But the program is billions of dollars over budget and years behind schedule -- and, many would argue, generations behind SpaceX in innovation.

The space agency's first three Artemis moon missions over the next three years -- including a human landing planned for 2025 -- are all set to travel aboard the SLS rocket and Orion capsule, which are being built by Boeing, Lockheed Martin, Northrop Grumman, Aerojet Rocketdyne and numerous other suppliers and engineering services firms. But with the SLS' first flight this year further delayed at least until late spring, concerns are growing that even if it succeeds, the system, at an estimated $2 billion per launch, could prove too costly for the multiple journeys to the moon that NASA will need to build a permanent human presence on the lunar surface.

That makes Starship, which conducted a successful flight to the edge of space last year, especially threatening to the contractors and their allies in Congress. As Starship progresses, it will further eclipse the argument for sticking with SLS, according to Rand Simberg, an aerospace engineer and space consultant. "Once the new system's reliability is demonstrated with a large number of flights, which could happen in a matter of months, it will obsolesce all existing launch systems," he said. "If SLS is not going to fly more than once every couple of years, it's just not going to be a significant player in the future in space, particularly when Starship is flown," he added.

An anonymous reader quotes a report from the New York Times: On March 4, a human-made piece of rocket detritus will slam into the moon. But it turns out that it is not, as was previously stated in a number of reports, including by The New York Times, Elon Musk's SpaceX that will be responsible for making a crater on the lunar surface. Instead, the cause is likely to be a piece of a rocket launched by China's space agency.

Last month, Bill Gray, developer of Project Pluto, a suite of astronomical software used to calculate the orbits of asteroids and comets, announced that the upper stage of a SpaceX Falcon 9 rocket was on a trajectory that would intersect with the path of the moon. [...] But an email on Saturday from Jon Giorgini, an engineer at NASA's Jet Propulsion Laboratory in California, changed the story. Mr. Giorgini runs Horizons, an online database that can generate locations and orbits for the almost 1.2 million objects in the solar system, including about 200 spacecraft. A user of Horizons asked Mr. Giorgini how certain it was that the object was part of the DSCOVR rocket. "That prompted me to look into the case," Mr. Giorgini said.

Part of a rocket is expected to crash into the far side of the moon on March 4. Initially thought to be a SpaceX rocket stage, the object may actually be part of a Long March 3C rocket [that launched China's Chang'e-5 T1 spacecraft on Oct. 23, 2014]. He found that the orbit was incompatible with the trajectory that DSCOVR took, and contacted Mr. Gray. [...] Mr. Gray now realizes that his mistake was thinking that DSCOVR was launched on a trajectory toward the moon and using its gravity to swing the spacecraft to its final destination about a million miles from Earth where the spacecraft provides warning of incoming solar storms. But, as Mr. Giorgini pointed out, DSCOVR was actually launched on a direct path that did not go past the moon. "I really wish that I had reviewed that" before putting out his January announcement, Mr. Gray said. "But yeah, once Jon Giorgini pointed it out, it became pretty clear that I had really gotten it wrong." There is still no chance of the rocket missing the moon, the report says.

"As for what happened to that Falcon 9 part, 'we're still trying to figure out where the DSCOVR second stage might be,' Mr. Gray said," according to the Times. "The best guess is that it ended up in orbit around the sun instead of the Earth, and it could still be out there. That would put it out of view for now."

This true story of a hammer, a feather, the Apollo 15 mission, and the answers to humanity's oldest questions about how stuff falls. From a report: Does a falling object move at a constant speed, or does it speed up? If you drop a heavy object and a light one at the same time, which will fall faster? The great thing about these two questions is that you can ask pretty much anyone and they will have an answer -- even if they are actually wrong. The even greater thing is that it's fairly simple to determine the answers experimentally. [...] OK, but what about dropping a rock and feather -- doesn't the rock hit first? Usually, the answer is yes. But let's replace the rock with a hammer and then just take a change of scenery and move the experiment to the moon. This is exactly what happened during the Apollo 15 lunar mission in 1971. Commander David Scott took a hammer and an eagle feather and dropped them onto the lunar regolith. Here's what happened: The feather and the hammer hit the ground at the same time.

Why did it happen? First, it is indeed true that even on the moon there is a greater gravitational force on the hammer than the feather. We can calculate this gravitational force as the product of mass (m in kilograms) and the gravitational field (g in newtons per kilogram). On the surface of the moon, the gravitational field has a value of 1.6 N/kg. If you put this expression in for the net force on a falling object, it looks like this: Fnet = - mg = ma; a = -g. Since both the gravitational force and the acceleration depend on the same mass, it's on both sides of the equation and cancels. That leaves an acceleration of -g. The hammer and the feather fall down with identical motions and hit the ground at the same time.

So, what's different about dropping something on the moon versus on Earth? Yes, there is a different gravitational weight on the moon -- but that's not the issue. It's the lack of air that makes the difference. Remember that Newton's second law is a relationship between the net force and the acceleration. If you drop a feather on the surface of the Earth, there are two forces acting on it. First, there is the downward-pulling gravitational force that is equal to the product of mass and the gravitational field. Second, there is an upward-pushing force due to the interaction with the air, which we often call air drag. This air drag force depends on several things, but the important ones are the object's speed and the size of the object. [...]

XKCD creator Randall Munroe has announced his latest science book: What If? 2: Additional Serious Scientific Answers to Absurd Hypothetical Questions, which will delve into new out-of-the-box questions that Munroe attempts to answer with hard scientific facts and research. From a report: What If? 2 follows 2014's original What If? book -- which itself was borne out of an XKCD spinoff blog -- that saw Munroe examine absurd questions (like whether you could build a jetpack that ran off downward-facing machine guns or if there's enough paint to cover the entire surface of the earth) with rigorous scientific accuracy, accompanied by Munroe's signature stick figure comics. The new volume will continue in What If?'s absurd scientific footsteps, attempting to answer new questions from readers like how you'd ride a fire pole from the moon to Earth, or what would happen if you tried to build a billion-story-high building or solve global warming by having everyone on earth open their freezer doors.

Astronomers said this week that a piece of a Falcon 9 rocket that was launched in February 2015 is currently on a trajectory to collide with the moon in just a few weeks. CBS News reports: The rocket left from Florida's Cape Canaveral and launched NOAA's Deep Space Climate Observatory, a project that allows researchers to maintain real-time data for more accurate space weather alerts and forecasts. According to NOAA, having that data is "critical," as space weather events "have the potential to disrupt nearly every major public infrastructure system on Earth." During that deployment, Falcon 9's second stage, which provides it with a second boost to reach its desired orbit, ran out of fuel to return to Earth, according to meteorologist and Ars Technica space editor Eric Berger. The second stage has been orbiting Earth ever since, and now, according to data gathered by astronomers, it's on track to hit the moon.

Bill Gray, who writes the Project Pluto software that is used by both amateur and professional astronomers, gathered data from those space observers over the past few weeks to predict just when the impact will occur. Based on the information he gathered, there will be a "certain impact" with the far side of the moon on March 4, he said. The rocket stage is currently floating away from Earth and outside of the moon's orbit on a "chaotic" orbit, Gray said, but in the coming days, it's expected to turn around and head back towards Earth. It made a "close lunar flyby" on January 5, but March 4 is when its path and the moon's will cross. Thankfully, there's no cause for concern, says Gray, noting that it's the "first unintentional case" of space junk hitting the moon that he's aware of. It may actually help researchers learn more about the moon's makeup if lunar orbiters are able to observe the crash site.

"If we can tell the [lunar orbiter] folks exactly where the crater is, they'll eventually pass over that spot and be able to see a very fresh impact crater and probably learn something about the geology (well, selenology) of that part of the moon," Gray said.