The Pilbara region of Western Australia is big, dry, and wide open. And it may contain the oldest cosmic “scar” on Earth: an impact crater gouged three and a half billion years ago.

Scientists discovered evidence of the crater during a brief expedition in 2021. They found some rock formations called shatter cones. Some of the cones are as tall as a house. The only known way to make them is in giant collisions with space rocks.

Follow-up work last year revealed many more of these formations. The cones were found in a rock layer that’s miles wide, but only a few dozen feet thick.

The layer also contains tiny “beads” that formed when molten rock was blasted high into the sky. The flight through the air sculpted droplets of the molten rock into balls.

Geologists found that the layer formed three and a half billion years ago, so that’s when the impact must have taken place – more than a billion years earlier than the previous record holder.

The asteroid could have been miles wide, and blasted a crater more than 60 miles across. The effects of the collision would have been felt around the world.

In fact, researchers say the impact could have helped shape the world. Major asteroid impacts could have traveled deep, churning things up far below the surface. That could have created the “seeds” that gave birth to the continents when Earth was young.

We’ll talk about potential future impacts tomorrow.

Script by Damond Benningfield

You can’t tell just by looking, but the universe undergoes constant change. Stars explode. Quasars flare up. Asteroids zip past Earth. And soon, astronomers will be able to generate super-high-definition movies of those changes almost every night of the year. That’s because a new telescope dedicated to “time-domain” astronomy is about ready to take its first looks at the heavens.

The telescope is the centerpiece of the Vera Rubin Observatory. It’s named for an astronomer who provided strong evidence for the existence of dark matter. It’s atop an 8700-foot mountain in Chile.

The telescope’s main mirror, which gathers and focuses starlight, is 8.4 meters across – almost 28 feet. It has a wide field of view, allowing it to photograph the entire southern sky every few nights. It’ll record its observations on the largest digital camera ever built – 3200 megapixels.

Astronomers will use those observations to learn more about dark energy and dark matter, and to map the Milky Way Galaxy. And they’ll watch for things that change. They’ll discover asteroids and comets – both close to Earth and deep in the outer solar system. They’ll see novas, supernovas, and other brilliant flare-ups. And the observatory will send out immediate notices of each new outburst, allowing other astronomers to make detailed follow-up observations – learning much more about our constantly changing universe.

Script by Damond Benningfield

Before astronauts could land and walk on the Moon, NASA had to be sure they could do three things: live in space for days at a time, catch and link up with other spacecraft, and work outside their ship. And it took stabs at two of those goals 60 years ago today, with a mission called Gemini 4.

  [AUDIO: 3, 2, 1, Ignition … Liftoff …]

Astronauts James McDivitt and Ed White were scheduled to spend four days in space. That was longer than the first seven American missions combined.

And White would make the first American spacewalk. He’d float outside the cabin for a few minutes, using a small “gun” of compressed air to move around.

And three and a half hours after launch, it was time to get started:

CAPCOM: Gemini 4, Hawaii capcom. We just had word from Houston, we’re ready to have you get out   whenever you’re ready. Okay, my feet are out. … Okay, I’m out.

The spacewalk went well – very well. [WHITE: I feel like a million dollars!] In fact, it went so well that White didn’t want it to end.

HOUSTON: The flight director says get back in!

     McDIVITT: This is Jim, you got any message for us?

     CAPCOM: Gemini 4, get back in!

     McDIVITT: Okay…

Actually working during a spacewalk turned out to be a lot harder than White had made it look. It took several more missions to work out the kinks. But the success of Gemini 4 helped make it possible for astronauts to walk on the Moon just four years later.

Script by Damond Benningfield

If you step outside at dawn on June third of 2033, you’ll see the planet Venus standing due east – the brilliant “morning star.” But if you don’t want to wait that long to experience that beautiful view, then take a look at dawn tomorrow – Venus will be standing in the same spot in the sky. Not only that, it stands at that spot in the sky every eight years.

In fact, anytime you see Venus – whether as the morning star or evening star – you can find it at that same spot eight years later. That’s because there’s a near-“resonance” in the orbital cycles of Earth and Venus. Venus completes 13 orbits around the Sun for every eight orbits that Earth makes. The ratio isn’t exact, but it’s quite close.

Thanks to that, Venus follows five repeating cycles across our sky. It’s like the planet is a toy train on a looping, winding track. It hits every point along the track with every cycle. If you plot that motion from the perspective of Earth, it traces out a flowing pattern like five rose petals.

The clockwork precision makes it easy to predict the entire sequence of Venus’s appearances. We know that it always remains in view in the morning sky for about 263 days, disappears for about 50 days, then moves into the evening sky.

So if you miss the view of Venus tomorrow, or the next day, or the day after that, just mark it in your calendar – and look for it in the same location eight years later.

Script by Damond Benningfield

The Moon has regular dates with the stars. It returns to the same position relative to the stars every 27 days and eight hours. As an example, the Moon cozied up to Regulus, the bright heart of the lion, on May 5th, and it does so again this evening – 27 days, eight hours later. This encounter is especially close as seen from the United States – the Moon and Regulus will appear to almost touch each other.

That time span is known as the lunar sidereal period – “sidereal” meaning “related to the stars.”

The planets have their own sidereal periods.

Mars, for example, returns to the same point relative to the stars every 22 and a half months. Tonight, Mars is well to the lower right of Regulus, and looks like an orange star. It’ll return to almost the same position in April of 2027. The match won’t be exact because our viewing angle to the Red Planet changes a bit from year to year.

The sidereal period is different from the period relative to the Sun – a difference caused by Earth’s own orbital motion. For the Moon, that period lasts 29 and a half days – the length of a cycle of phases. And for Mars, the Sun-related period is almost 26 months. That’s how long it takes Mars to return to the same angle from the Sun – part of the precise but sometimes confusing motions in the night sky.

More about the motions of the planets tomorrow.

Script by Damond Benningfield

To the more poetic among us, summer is a time of soft breezes, warm nights, and fireflies: The livin’ is easy, the breeze makes us feel fine, the warm Sun shines kindly upon us.

But there’s less poetry in the summers on Mars – especially in the northern hemisphere, where summer began on Thursday. It stays cold, and the only fireflies are occasional meteors blazing through the night.

Like the seasons on Earth, those on Mars are caused by the planet’s tilt on its axis. Northern summer begins when the north pole dips most directly toward the Sun. But Mars’s orbit is much more lopsided than Earth’s, so there’s a much greater change in the planet’s distance from the Sun. Mars is farthest from the Sun during northern summer. So the summer stays fairly cool.

Summers and winters tend to be quiet times in the planet’s thin atmosphere. Big dust storms fire up in spring and fall, sometimes covering the whole planet. But they settle down by the start of summer. Mars does see more “dust devils” during summer – whirlwinds that can tower miles high.

Northern summer will last for 178 Mars days – not giving way until the start of autumn exactly six months from now.

Mars is close to the upper left of the Moon at nightfall, and looks like a fairly bright orange star. The true star Regulus is farther along that line. More about this lineup tomorrow.

Script by Damond Benningfield

The United States plans to send astronauts to the Moon later in this decade, aiming toward a permanent lunar base. But experience shows that plans come and go. In fact, if all the plans for lunar exploration had actually come about, we’d be skittering all across the Moon today.

In 1958, for example, the Air Force developed Project LUMAN, a comprehensive plan for human spaceflight. It would culminate with a single astronaut landing on the Moon. Later, the service developed another plan – LUMEX. It called for three astronauts to travel to the Moon using a giant new booster and a streamlined spaceship. The Army developed its own plan, involving a space station and other steps.

All of those plans died – in part because human spaceflight was turned over to a new civilian agency: NASA.

And NASA had its own false steps. It studied using its two-man Gemini spacecraft for lunar missions before settling on Apollo. And even then, some of its plans were scuttled; the final three Apollo missions were scrapped, in 1970.

President George W. Bush proposed lunar missions as part of the Constellation program. It was nixed by President Obama. But some of its hardware has been kept for Artemis – which plans to send astronauts to the Moon in the next few years.

Look for the Moon in the west at nightfall. The twin stars of Gemini stand to its lower right, with Mars to its upper left – another planned destination for human explorers.

Script by Damond Benningfield

Globular clusters are the oldest members of the galaxy. They’re tight balls of hundreds of thousands of stars, most of which were born when the universe was no more than a couple of billion years old. Their most-massive stars have long since died. And most of the stars that remain are cool and faint. So a globular tends to be fairly quiet and calm. But that doesn’t mean that things don’t change.

Consider Messier 13. It’s in Hercules, which is high in the east at nightfall. Under dark skies, the cluster is just visible to the unaided eye, looking like a faint, fuzzy star.

The cluster is about 25,000 light-years away, and it contains up to half a million stars. But the stars at the edge of the cluster aren’t held as tightly as those in the middle. So the gravity of the rest of the galaxy can pull some of them away. In fact, astronomers have identified a few dozen stars that appear to be escapees from M13.

But the cluster also can grab stars from the space around it. One especially young star probably became a member of the cluster that way.

And stars inside the cluster can change. Some of them merge, forming bright, blue stars that look much younger. And stars die. M13’s brightest member is dying right now. It’s about as massive as the Sun, but it’s puffed up to dozens of times the Sun’s diameter. Soon, it’ll blow away its outer layers, leaving only its tiny, dead core – one more change in an ancient family of stars.

Script by Damond Benningfield

Three of the four big moons of Jupiter appear to have something in common: oceans of liquid water below their crusts. For Europa, the ocean is considered a slam dunk. The case is also strong for Ganymede. But the case for the third moon, Callisto, is the weakest.

Callisto is about 3,000 miles in diameter – bigger than our own moon. And it’s more heavily cratered than any other large body in the solar system. That indicates that the surface of Callisto is pretty much dead. But things might be different far below the surface.

In the 1990s, the Galileo spacecraft flew near Callisto eight times. Its measurements of the magnetic field around the moon hinted that a salty ocean was sloshing around inside. But those observations also could be produced by an electrically charged layer of Callisto’s thin atmosphere.

In a recent study, though, scientists looked at all of Galileo’s observations, and used computer models to understand them. The work suggested that there is an ocean. It could be dozens of miles deep. But it’s buried beneath an icy crust that could be hundreds of miles thick.

Two spacecraft that are en route to Jupiter will fly close to Callisto many times. Their observations should tell us for sure whether an ocean is sloshing below Callisto’s battered surface.

Jupiter stands below our moon in the early evening twilight. It looks like a bright star.

Script by Damond Benningfield

If stars had trophy cases, Vega’s would be packed. The leading light of Lyra was the first star other than the Sun to have its picture taken, the first to have its spectrum taken, and the first with a published measurement of its distance.

Vega is impressive in many ways. It’s more than twice the size and mass of the Sun, and about 50 times the Sun’s brightness. It’s encircled by a wide belt of dust, produced by collisions between big chunks of ice and rock. In about 12,000 years, it’ll serve as the Pole Star. And in about 200,000 years it’ll become the brightest star in the night sky.

Vega first had its picture taken in 1850. In 1872, an astronomer took a picture of its spectrum, spreading its light into its individual wavelengths. A spectrum reveals a star’s composition, motion, and much more.

In 1838, Russian astronomer Friedrich von Struve published Vega’s parallax – the first publication for any star. He plotted its position when Earth was on opposite sides of the Sun. That revealed a tiny shift against the background of more-distant objects. That shift revealed a distance of about 26 light-years – just one light-year off the modern measurement.

Vega is low in the east-northeast at nightfall and climbs high overhead during the night. It’s the fifth-brightest star in the night sky, so you can’t miss it – a beautiful star with a case full of trophies.

Script by Damond Benningfield