Venus is a tricky place to study because it’s shrouded in a thick atmosphere that hides its surface. And if you can’t even see its surface, imagine how difficult it must be to study the interior of Venus. But scientists have been making steady progress towards understanding the interior of the planet, and learn about the core of Venus.
Here on Earth, scientists study the core of the planet by measuring how seismic waves move through the planet after earthquakes. As they pass through the different layers of the Earth’s interior; the core, the mantle, and the crust, the waves reflect or bend depending on the change of density that they’re passing through. Well, the surface of Venus is hot enough to melt lead, and spacecraft are destroyed within a few hours of reaching the surface of Venus, so no readings have been gathered about Venus’ core directly.
Instead, scientists assume that the core of Venus exists based on calculations of its density. The density of Venus is only a little less than the density of Earth. This means that Venus probably has a core of metal about 3,000 km across, surrounded by a 3,000 km thick mantle and a 50 km thick crust.
Scientists aren’t sure if the core of Venus is solid or liquid, but they have a few hints. That’s because Venus doesn’t have a planet wide magnetic field like the Earth. It’s believed that the Earth’s magnetic field is generated by the convection of liquid in the Earth’s core. Since Venus doesn’t have a planetary magnetic field, it’s possible that Venus’ core is made of solid metal, or maybe there isn’t enough of a temperature gradient between the inner and outer core to made this convection happen.
It’s believed that a global resurfacing event that occurred about 300-500 million years ago might have something to do with this. The entire surface of Venus was resurfaced, shutting down plate tectonics. This might have led to a reduced heat flux through the crust, trapping the heat inside the planet. Without the big heat difference, there’s little heat convection, and so no magnetic field coming from the core of Venus.
Take a look at Venus in even the most powerful telescope, and all you’ll see is clouds. There are no surface features visible at all. It wasn’t until the last few decades, when radar equipped spacecraft arrived at Venus, that scientists finally had a chance to study the geology of Venus in great detail.
Spacecraft like NASA’s Magellan mission are equipped with radar instruments that let it penetrate down through the clouds on Venus and reveal the surface below. Magellan found that the surface of Venus does have many impact craters and evidence of past volcanism. But the total number of craters showed that the surface of Venus is actually pretty young. It’s likely that some catastrophic event resurfaced Venus about 300-500 million years ago, wiping out old craters and volcanoes.
Unlike Earth, Venus doesn’t have plate tectonics. It’s possible that the planet had them in the ancient past, but rising temperatures shut them down and helped the planet go into a runaway greenhouse cycle. Carbon on Earth is trapped by plants, and is then recycled into the Earth through plate tectonics. But on Venus, the tectonic system shut down, so carbon was able to build up to tremendous levels. This cycle thickened the atmosphere, raised temperatures with its greenhouse effect, releasing more carbon, raising temperatures even higher… etc.
There are volcanoes on Venus; scientists have identified more than 100 isolated shield volcanoes. And there are thousands and maybe even millions of smaller volcanoes less than 20 km across. Many of these have a strange dome-shaped structure, believed to have formed when plumes of magma thrust the crust upward and then collapsed.
Scientists can’t be exactly sure what the internal structure of Venus is like, but based on its density, Venus is probably similar to Earth in composition. It’s believed to have a solid or liquid core of metal 3,000 km across. This is surrounded by a mantle of rock 3,000 km thick, and then a thin crust of solid rock about 50 km thick.
One big difference between Earth and Venus is the lack of a planetary magnetic field at Venus. It’s believed that the Earth’s magnetic field is driven by the convection of liquid metal at the Earth’s core. If true, it means that Venus probably doesn’t have the same kind of temperature differences at its core, and lacks the convection to sustain a planetary magnetic field.
Venus is often referred to as Earth’s twin planet (evil twin planet is more like it, when you consider the scorching temperatures). It’s almost the same size, mass, gravity and overall composition. The composition of Venus is pretty similar to Earth, with a core of metal, a mantle of liquid rock, and an outer crust of solid rock.
Unfortunately, scientists have no direct knowledge about Venus composition. Here on Earth, scientists use seismometers to study how seismic waves from earthquakes propagate through the planet. How these waves bounce and turn inside the Earth tell scientists about its composition. Since the surface of Venus is hot enough to melt lead, and no spacecraft have survived on the surface for longer than a few hours, there just isn’t the information about Venus’ internal composition.
Scientists can calculate the density of Venus, though. Since it’s similar to Earth, and the other terrestrial planets, scientists guess that the internal structure of Venus is similar to Earth. One of the big differences between our two planets, however, is the lack of plate tectonics on Venus. For some reason, plate tectonics on Venus shut down billions of years ago. This has prevented the interior of Venus from losing as much heat as the Earth does, and could be the reason Venus doesn’t have an internally generated magnetic field.
Before spacecraft missions were sent to Venus, scientists had no idea what the composition of Venus was. They could calculate the planet’s density, but the surface of Venus was obscured by dense clouds. Spacecraft equipped with radar were able to penetrate the thick clouds and map out features on the planet’s surface, showing that it has impact craters and ancient volcanoes. It’s believed that Venus went through some kind of global resurfacing event about 300-500 million years ago, which is the age of the planet’s surface (calculated by the number of impact craters).
The crust of Venus is thought to be about 50 km thick, and composed of silicious rocks. Beneath that is the mantle, which is thought to be about 3,000 km thick. The composition of the mantle is unknown. And then at the center of Venus is a solid or liquid core of iron or nickel. Since Venus doesn’t have a global magnetic field, scientists think that the planet doesn’t have convection in its core. The planet doesn’t have a large difference in temperature between the inner and outer core, and so the metal doesn’t flow around and generate a magnetic field.
ISS as seen from departing space shuttle Endeavour. Credit: NASA TV
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A great opportunity tonight (July 28) to see three spaceships cross the sky at once! Endeavour just undocked from the ISS today, so they will be close to each other, plus there’s another spaceship lurking nearby: a Progress re-supply ship ready to dock with the ISS. How can you find out when and where to look for the three spacecraft? There are a couple of different websites that provide real-time tracking data and information about the ISS sighting opportunities. See below for more info.
The image above is a screenshot from NASA TV of the ISS as Endeavour undocked. Notice the shadow of the shuttle on the ISS solar arrays!
NASA has a Quick and Easy Sightings by City site, where you just search for your country and city which provides local times and the location in the sky where the station will be visible.
The European Space Agency also provides their ISS: Where Is It Now site that also allows you to select your country and city to find the station’s location.
The Heaven’s Above website (which also powers ESA’s site) is also an excellent site to find out when the ISS, as well as all sorts of other satellites and other heavenly sights will be visible. At Heaven’s Above, you can plug in your exact latitude and longitude, so if you live in a remote area, you’ll be able to have exact times and locations to look for satellites instead of relying on information for the nearest city.
Additionally, you can get a notification on Twitter when the space station will be zooming over your skies. Follow Twisst. (Thanks to big ian for the reminder of this new Twitter addition!)
Here’s wishing everyone clear skies and great views!
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As space shuttle Endeavour undocks from the International Space Station today (Tuesday), now is a good time to look back at the very successful STS-127 mission. Here’s some great images which tell the story of the mission. Above, astronaut Tim Kopra is pictured in the forward port side area of Endeavour’s cargo bay during the first of five planned spacewalks performed by the STS-127 crew. Kopra is now part of the ISS crew, and is staying onboard the space station to serve as flight engineer.
Moon rock on board the ISS. Credit: NASA
Of course, during this mission we celebrated the 40th anniversary of the Apollo 11 Moon landing. Fittingly, there was a Moon rock on board the ISS. The 3.6 billion year-old lunar sample was flown to the station aboard Space Shuttle mission STS-119 in April 2009. NASA says the rock, lunar sample 10072 serves as a symbol of the nation’s resolve to continue the exploration of space. It will be returned on shuttle mission STS-128 to be publicly displayed.
Here’s a view of the newly installed “front porch” of the Kibo lab, which is actually the Japanese Experiment Module – Exposed Facility (JEF). This platform will hold experiments designed to work outside the protective confines of the station, exposing them to the space environment. The JEF was installed by the astronauts during this mission. Dave Wolf during an EVA. Credit: NASA
During the second STS-127 spacewalk, astronaut Dave Wolf worked outside bringing the Linear Drive Unit (LDU) and two other parts to the station’s External Stowage Platform 3 for long-term storage. Wolf is near the end of Canadarm2, which is anchored on the ISS. Arms in space. Credit: NASA
Speaking of the robotic arms, here’s a view of both the space station and space shuttle robotic arms as seen from inside the Kibo laboratory. A portion of the Japanese Experiment Module – Exposed Facility is also visible. The blackness of space and Earth’s horizon provide the backdrop for the scene. Tom Marshburn during an EVA. Credit: NASA
Astronaut Tom Marshburn makes his second spacewalk on July 24, along with Christopher Cassidy, out of frame. Eleven other astronauts and cosmonauts remained inside the International Space Station and the shuttle while the two astronauts worked outside. Astronauts share a lunch on the ISS. Credit: NASA
In total, there were 13 astronauts on board the ISS, a record for the amount of astronauts in one vehicle. Pictured, clockwise from bottom right, are astronauts Christopher Cassidy and Mike Barratt, with Russian Federal Space Agency cosmonaut Roman Romanenko, an unidentified crew member, Japanese Aerospace Exploration Agency astronaut Koichi Wakata (floating above), Canadian Space Agency astronauts Robert Thirsk and Julie Payette, European Space Agency astronaut Frank De Winne, and astronaut Christopher Cassidy. Either out of frame or not clearly seen are astronauts Mark Polansky, Doug Hurley, Dave Wolf, Tim Kopra and Tom Marshburn, plus Russian Federal Space Agency cosmonaut Gennady Padalka. ISS as seen from departing space shuttle Endeavour. Credit: NASA TV
This screen shot shows the ISS as seen as Endeavour departed from the station on July 28. The views of both the ISS and shuttle were stunning. We’ll post the high-resolution versions when they become available. Notice the shadow of the space shuttle on the space station solar arrays! Amazing! Endeavour's launch. Credit: NASA
And now we’re back to the beginning of the mission. Liftoff for the STS-was at 6:03 p.m. (EDT) on July 15, 2009 from launch pad 39A at NASA’s Kennedy Space Center. The storm clouds stayed far enough away so that Endeavour and her STS-127 crew finally on its sixth attempt. Watch a replay of the launch here.
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The average circumference of Venus is 38,025 km.
Need some comparison? The average circumference of Earth is 40,041 km. And then if you compare the two numbers, you find that the circumference of Venus is about 95% the circumference of Earth.
If you’ll notice at the top of the article, I specified that we’re talking about the “average circumference”. That’s the number if you average out all the circumference measurements around the planet. This is normally very important when you measure the circumference of planets since they’re often spinning quite rapidly. This rotation causes them to flatten out and bulge around the equator. This means that the equatorial circumference is larger than the circumference if you measure it from pole to pole.
The average (or mean) circumference on Earth is 40,041 km. The equatorial circumference is 40,075 km, and the polar circumference is 40,008 km. So you can see, that’s a pretty big difference, and the average is very important. But here’s the thing. Venus rotates so slowly that it doesn’t bulge at the equator. While the Earth turns once on its axis every 24 hours, Venus takes 243 days to complete a day – that’s even longer than a year on Venus!
Need your numbers in miles? No problem. The circumference of Venus in miles is 23,628 miles.
The density of Venus is 5.204 grams per cubic centimeter.
Need some kind of comparison? The density of Earth is 5.515 g/cm3. So Venus is definitely less dense than Earth. And it’s even less dense than Mercury. Of course, it’s much more dense than any of the outer planets, like Jupiter or Saturn.
Scientists think that Venus has an interior structure similar to Earth, with a metal core, rocky mantle, and an outer crust. But these assumptions come purely from the density calculations. Here on Earth, scientists study the interior structure of the planet by using seismographs, and studying how seismic waves from earthquakes travel through the Earth. Since the surface of Venus is hot enough to melt lead, there’s no way to leave scientific equipment on the surface for any period of time to study the interior of the planet.
With its lower density, Venus has a lower mass than Earth. In fact, the mass of Venus is only about 81% the mass of Earth. And it’s also a little smaller than Earth. This means that the surface gravity of Venus is only 90% of what you would experience on Earth.
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The axial tilt of Venus is 177.3°. That’s a bit of a confusing number, so let’s figure out what’s going on here. Compare this number to the Earth’s axial tilt of 23.5°. Our tilt gives us such different seasons between summer and winter, so you’d expect that Venus’ much larger tilt would cause more extreme seasons.
Nope. But if you remember your high school geometry, you’ll realize what’s going on. A full circle is 360°. Half a circle is 180°. So if you subtract 177.3° from 180°, you get 2.7°. In other words, Venus is actually only tilted away from the plane of the ecliptic by only 2.7°. Venus is actually completely upside down – almost perfectly upside down.
In fact, Venus is the only planet in the Solar System that rotates backwards compared to the other planets. Seen from above, all the planets are turning in a counter clockwise direction. That’s why Asia sees the Sun first, then Europe, and then the Americas. Mars is the same, and so is Mercury, but Venus is rotating clockwise.
It’s possible that Venus was knocked upside down by a massive impact early in its history. it’s also possible that Venus just slowed down through tidal locking with the Sun, and was somehow spun slowly backwards through its interactions with the other planets.
Here on Earth, the axial tilt is responsible for the seasons. When it’s winter in the northern hemisphere, the north pole is tilted away from the Sun, and less of the Sun’s radiation falls on every square meter of ground. The opposite is true in the summer. Without a significant axial tilt, Venus doesn’t experience seasons like this. The temperature of Venus is a nice even 462°C everywhere on the whole planet.
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As Japan’s first astronaut to spend long duration missions on board the International Space Station, Koichi Wakata has had the opportunity to do all sorts of interesting experiments the past few months. For example, he conducted several different cellular growth and crystal growth experiments, and has even flown a magic carpet in space. One other experiment has been – shall we say – kept under wraps. Wakata has been wearing the same underwear on board the ISS for two months.
“(For) two months I was wearing these underwear and there was no smell and nobody complained,” Wakata, speaking in Japanese, said through an interpreter during a press conference this weekend from the ISS. “I think that new J-ware underwear is very good for myself and my colleagues.”
Wakata has been wearing special underwear and other clothing called “J-ware” designed for the Japanese space agency. According to an article in Discovery News, the clothes are treated with antibacterial and deodorizing materials. In addition to odor control, the clothes are designed to absorb water, insulate the body and dry quickly. They also are flame-resistant and anti-static — as well as comfortable and attractive.
Typically, clothes can only be worn for a few days in space, and especially the clothing worn by astronauts as they exercise. Since there’s no laundromat in space, the clothing is discarded as garbage.
Astronaut Takao Doi, who flew with a shuttle crew last year to deliver Japan’s Kibo laboratory to the station, exercised as much as his crewmates, but his clothes stayed dry.
Wakata’s clothes include long- and short-sleeved shirts, pants, shorts and underwear. Special socks have a separate pouch for the big toes so the astronauts can use their feet like an extra pair of hands, helpful for anchoring themselves on the floor while doing work on the station.
Originally, Wakata was scheduled to wear the underwear for just a couple of weeks. But obviously, he decided to go the long duration route. Proposed Japanese space toilet. Credit: JAXA
At least he wasn’t testing this other option proposed by JAXA. Read more about these special underwear here.
Wakata heads home with the crew of the STS-127 mission, undocking from the ISS today. The first landing opportunity is Friday, July 31.
Astronaut Scott Altman speaking to children at the Lakeview Museum of Arts and Sciences. Photo: Nancy Atkinson
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Astronaut Scott Altman, commander of the recent servicing mission to the Hubble Space Telescope said the independent review of NASA’s current plans is allowing both the space agency and the nation to step back, contemplate and plan the future. “The new administration wants to take a good hard look at the direction of future of the space program and I endorse that,” Altman said. I think we’ll come out of this with a more focused and hopefully a stronger movement forward. And the folks working on Constellation have the chance to take a breath while the Augustine Commission is at work and I’m looking forward to hearing what they have to say.”
The veteran astronaut worked on helping to develop the Constellation program before he was assigned to the Hubble servicing mission, and he looks forward to returning to that task, whether it be the Ares and Orion vehicles or another incarnation of the next space vehicles. When asked about his future plans, Altman said. “I think I will go back and work on the next generation vehicle as we work those designs. Will I get to stick around and maybe fly them? I don’t know, that’s another five or six years — we’ll see. But I’m loving what I’m doing and it’s great to be an astronaut at NASA.” Scott Altman speaks to reporters. Photo: Nancy Atkinson
The Augustine Commission is holding an open meeting on Tuesday in Houston, and another on July 29 in Huntsville, Alabama, to allow public input on the course NASA should be taking. Altman likes that the Commission is readily taking public comment.
“It’s always good,” he said. “The space program is a manifestation of the country’s national will, what we want to do. I think it is important that NASA stay connected with people. There should be a place where the public can let NASA know how they think we’re doing. And we (NASA) need to make sure we let them know what we are doing, so we need to make sure the communication goes both ways.”
Hubble Images of Jupiter Impact Site
Altman was asked if he had seen the first Hubble image released to the public since the servicing mission, a surprise observation of the recent impact on Jupiter. “The pictures they took of Jupiter were awesome,” he said “The other great thing about seeing those pictures is that we know our repairs worked, so it’s nice to see the success of our mission.”
The Wide Field Camera 3, which took the Jupiter image, was one of the first tasks for Altman and his STS-125 crew to repair, and the repair provided some initial drama for the mission. “I thought it wasn’t going to come out,” he said. “We came so close to being stuck with our very first thing not working out but I was thrilled when the old camera came out and the new went in. And now to hear that it’s working they way it should, we’re all thrilled.”
Altman said he and his crew were able to see other new images taken by the refurbished Hubble Space Telescope while at a visit to the Space Telescope Science Institute last week, and hinted the images may be released to the public soon. “We did get a sneak peak at some of the images they are starting to take and I think when they have an early release of them, you should all watch because it’s going to be incredible,” he said.
Mission Memories
Altman said the most memorable part of the STS-125 mission was when crewmate Mike Massimino had to tear a handle off the telescope in order to proceed with the repair of the STIS instrument. Massimino and spacewalking partner Michael Good spent hours struggling to remove a stuck bolt from a handrail on the telescope. Finally mission control told Massimino to just tear the handrail off.
“I was with the rest of the crew at the edge of the window looking out when Mike broke the handle off,” said Altman. “That was pretty amazing to watch. But I think it shows the benefit of having people in space who can respond to things that you didn’t think were going to happen.” Scott Altman makes a presentation at the Lakeview Museum in Peoria IL. Photo: Nancy Atkinson
Altman presented the museum with pictures and an item he flew in space. “When we fly in space we are able to take a few things with us,” he said. “One of the things that I took along was this Illinois flag. So it’s got 5.3 million miles on it, 197 orbits, but no frequent flyer miles! But I wanted to present it to the museum along with a few pictures from the mission as a way of saying thanks for the inspiration that started here for me, and starts for so many other people. And, as you kids here look to follow your dreams and reach for the stars, you never really know where you might end up, but there are some pretty cool places out there that you might visit, I know I have. It’s really an honor for me to be back here. I’m so thrilled and I just want to say thank you to the museum for the great work that you do, and I know you’re about to do a lot more in the near future in the new facility.
The Lakeview Museum will be part of a new 81,000-square-foot Peoria Riverfront Museum that will feature a 3-D IMAX Theatre, state-of-the-art planetarium, and other educational and cultural activities.
