Universe Today

August 4, 2009January 24, 2021 by Nancy Atkinson

LCROSS Sees Life on Earth

LCROSS UV/Visible spectrum. Credit: NASA

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The LCROSS spacecraft took a look back at Earth, and guess what it saw? Evidence of intelligence? Not so much. But it did see evidence of life. On Aug. 1, 2009, the LCROSS spacecraft took a gander at Earth to help calibrate and test its science payload. During the Earth observations, the spacecraft’s spectrometers were able to detect the signatures of the Earth’s water, ozone, methane, oxygen, carbon dioxide and possibly vegetation.

Phil Plait explained on Bad Astronomy that this spectrum covers part of the ultraviolet and visible range of light, and this type of observation with better instruments in the future could help us find life on other planets. Phil wrote. “You can see that LCROSS clearly detected ozone (O3) and water, which you might see on any old planet. But it also saw a feature that is from free oxygen (O2), something you don’t see just anywhere .… The only reason we have a lot of it in our air (more than 20% of the Earth’s atmosphere is O2) is because we have life in the form of plants.” Check out Phil’s post here.

The spacecraft also took these images of Earth, again, helping to refine camera exposure settings, check instrument pointing alignment, and check radiometric and wavelength calibrations.

LCROSS is in an elongated Earth orbit, and on course to impact the Moon’s south pole in October. From its current vantage point of 223,700 miles (360,000 km) from Earth, the LCROSS science team changed exposure and integration settings on the spacecraft’s infrared cameras and spectrometers and performed a crossing pattern, pushing the smaller fields of view of the spectrometers across the Earth’s disk. At this range, the Earth was approximately 2.2 degrees in diameter.

“The Earth-look was very successful,” said Tony Colaprete, LCROSS project scientist. “The instruments are all healthy and the science teams was able to collect additional data that will help refine our calibrations of the instruments.”

An additional Earth-look and a moon-look are scheduled for the remainder of the cruise phase of the mission.

Sources: NASA, Bad Astronomy

August 4, 2009December 24, 2015 by Nancy Atkinson

First Tweets from the ISS

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Listen my children and you shall hear
Tweets coming from up above our Earthly sphere.

The newest International Space Station astronaut has started Tweeting from space. Tim Kopra is the first ISS crew member to use the social media tool Twitter to discuss living and working in orbit. Kopra (@Astro_Tim) recently joined the Expedition 20 crew after arriving July 17 aboard space shuttle Endeavour. But the coolest thing is that his first Tweets’ origin was “from Mobile Web.” Yep, from the ISS, that’s really mobile.

But of course, there isn’t really “the web” up on the space station. But Kopra will sent down his Tweets messages to mission control in Houston, and they will post them on Twitter.
NASA says Kopra will provide followers with a unique perspective as an Expedition 20 flight engineer and member of the Army. He is an Army aviator and West Point graduate. He periodically will answer questions submitted on the Army’s Web site. To submit questions and view Kopra’s answers, visit the US Army’s website

This is Kopra’s first spaceflight. He completed his first spacewalk July 18 during the STS-127 mission. Kopra is in orbit with station Commander Gennady Padalka and Roman Romanenko — both Russian cosmonauts — and NASA astronaut Mike Barratt, European Space Agency astronaut Frank DeWinne and Canadian Space Agency astronaut Bob Thirsk.

As of this writing, Astro_Tim has close to 5,000 followers.

You can also follow Universe Today and Nancy on Twitter.

Source: NASA

August 4, 2009December 24, 2015 by Nancy Atkinson

Plains of Titan to be Named for “Dune” Novels

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Titan’s mysterious dark plains will be named after planets in the series of “Dune” science fiction novels by author Frank Herbert. The US Geological Survey Astrogeology Science Center announced the first plain or “planitia” given a name will be designated as Chusuk Planitia. Chusuk was a planet from the Dune series, known for its musical instruments. Chusuk Planitia on Titan is located at 5.0S, 23.5W, and in the picture here is the small, dark area next to the “C” of Chusuk.

Download a large map of Titan with the named features (pdf file).

The Cassini spacecraft has enabled us to finally see these dark plains on Titan. This moon is enveloped by an orange haze of naturally produced photochemical smog that frustratingly obscured its surface prior to Cassini’s arrival. Since 2004, the spacecraft’s observations have taken the study of this unique world into a whole new dimension.

Crescent Titan. Credit: NASA/JPL/Space Science Institute

One of Cassini’s latest images of Titan looks down on the north pole of Titan, showing night and day in the northern hemisphere of Saturn’s largest moon.

This view is centered on terrain at 49 degrees north latitude, 243 degrees west longitude. The north pole of Titan is rotated about 23 degrees to the left and it lies on the terminator above and to the left of the center of the image. Titan is 5,150 kilometers, or 3,200 miles across.

This natural color image was created by combining images taken with red, green and blue spectral filters. The images were obtained with the Cassini spacecraft wide-angle camera on June 6, 2009 at a distance of approximately 194,000 kilometers (121,000 miles) from Titan. Image scale is 11 kilometers (7 miles) per pixel.

Titan is one of the most Earth-like world we have found in our solar system. With its thick atmosphere and organic-rich chemistry, Titan resembles a frozen version of Earth, several billion years ago, before life began pumping oxygen into our atmosphere.

Cassini has revealed that Titan’s surface is shaped by rivers and lakes of liquid ethane and methane which forms clouds and occasionally rains from the sky as water does on Earth. Winds sculpt vast regions of dark, hydrocarbon-rich dunes and plains around Titan’s equator and low latitudes.

Source: USGS, Cassini website.

Hat tip to Emily Lakdawalla!

August 4, 2009December 24, 2015 by Fraser Cain

Earth’s Twin

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Scientists call Venus Earth’s twin planet and for good reason. Our two planets are similar in size, mass, density, gravity, and composition. Of course, they have some enormous differences as well; differences that would kill you instantly if you tried to step foot on Earth’s twin planet. Earth’s evil twin planet, maybe.

Let’s look at the similarities first. For starters, the size of Venus is very close to Earth. The diameter of Venus is 12,103.6 km. That’s only 95% of the Earth’s diameter of 12,756.2 km. If you put the two planets side by side, you’d have a hard time telling which one’s bigger.

The volume of Venus is 85.7% the volume of Earth, and it has 90% of the Earth’s surface area. The mass of Venus is 81.5% the mass of the Earth, and even the force of gravity is only 90% of what you experience here on Earth.

The composition of the two planets is similar too. Both have metal cores surrounded by a mantle of silica rock, and then a thin crust. There are some differences here, though. Earth’s core has convection which generates the planetary magnetic field, while Venus doesn’t have a similar magnetic field. Earth has plate tectonics, which help release heat from within the planet, while Venus doesn’t.

But there are bigger differences. And this is where it’s better to consider Venus as an evil twin planet. The temperature of Venus across the whole planet is 461.85 °C. That’s hot enough to boil lead! Spacecraft from Earth have only lasted a couple of hours at maximum because of the incredible temperatures. In fact, Venus is the hottest planet in the Solar System.

And if the temperature isn’t bad enough, the air pressure is even worse. The atmospheric pressure on the surface of Venus is 93 times higher than what you’d experience on Earth. In fact, you’d have to travel a kilometer beneath the surface of the ocean to experience that kind of pressure. While Earth’s atmosphere is made up of oxygen and nitrogen with trace amounts of carbon dioxide, Venus’ atmosphere is 96.5% carbon dioxide with the rest nitrogen. It has clouds of sulphuric acid that rain down to add to the planet’s lethality.

Earth has vast reserves of water, while Venus is almost completely dry. There are no reserves of water on the surface of Venus, and just a trace amount of water in its atmosphere. Because Venus doesn’t have a global magnetic field, it’s constantly pummeled by the Sun’s solar wind, which strips the lightest elements out of its atmosphere. Satellites have detected a constant stream of hydrogen atoms streaming away from Venus, lost from the planet forever.

And just one last difference, Earth has the Moon, but Venus has no moons. It might have had a moon in the past, but it’s believed to have crashed into the planet a long time ago.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

References:
NASA Solar System Exploration: Venus
NASA Solar System Exploration: Earth

August 4, 2009February 6, 2017 by Fraser Cain

Characteristics of Venus

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Venus is the second planet from the Sun, and considered in many ways to be a twin planet of Earth. It has a similar size, mass, density and gravity, as well as a very similar chemical composition. In other ways, Venus is very different than Earth, with its high surface temperature, crushing pressure, and poisonous atmosphere. Let’s take a look at some of the characteristics of Venus.

As I said at the beginning, Venus is the second planet from the Sun. It orbits at an average distance of 108 million km from the Sun, taking almost 225 days to complete one revolution around the Sun. One of the strange characteristics of Venus is that it’s actually rotating backwards from the rest of the planets. Seen from above, all of the planets rotate counter-clockwise, but Venus turns clockwise on its axis. Even stranger, a day on Venus lasts 243 days, which is longer its year.

In terms of size, Venus is quite similar to Earth. Its radius is 6,052 km (95% the size of the Earth). Its volume is about 86% the volume of Earth, and its mass is 4.87 x 10²⁴ kg, which is about 82% the mass of the Earth. The gravity on Venus is 90% the gravity on Earth, so if you could actually walk around on the surface of Venus, the gravity would feel very similar to Earth.

It’s when you get to the atmosphere of Venus that you see that the planet is very different from Earth. The temperature on the surface of Venus is a blistering 462 °C. That’s hot enough to melt lead! Furthermore, the atmospheric pressure on the surface of Venus is 92 times Earth pressure. You would have to travel a kilometer down beneath the surface of the ocean on Earth to feel that kind of pressure here. Venus’ atmosphere is composed almost entirely of carbon dioxide (97%), and it’s this thick atmosphere that acts like a blanket, keeping Venus so hot.

Venus has no water on its surface, and very little water vapor in its atmosphere. Scientists think that the runaway greenhouse effect that makes Venus so hot today boiled away its oceans long ago. Since Venus lacks a planetary magnetic field, the Sun’s solar wind was able to blast the hydrogen atoms out of Venus’ atmosphere and into space. Venus can never be cool again.

Most of the surface of Venus is covered by smooth volcanic plains, and its dotted with extinct volcanic peaks and impact craters. Venus has much fewer impact craters than other planets in the Solar System, and scientists have estimated that some event resurfaced Venus between 300-500 million years ago, wiping out all of the old impact craters and volcanoes.

Venus has no moons or rings.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

Reference:
NASA Solar System Exploration: Venus

August 4, 2009February 22, 2023 by Fraser Cain

Landings on Venus

The first color pictures taken of the surface of Venus by the Venera-13 space probe. Credit: NASA — The first color pictures taken of the surface of Venus by the Venera-13 space probe. The Venera 13 probe lasted only 127 minutes before succumbing to Venus's extreme surface environment. Part of building a longer-lasting Venus lander is figuring out how to power it. Credit: NASA

Venus might look like a virtual twin of the Earth in terms of size, but its temperature and atmosphere make it very different from the Earth. The temperatures can reach almost 500°C, and the atmospheric pressure is almost 100 times what you would experience on the surface of Earth. With such a terrible environment, you might be surprised to know that spacecraft have landed on Venus (although, they sure didn’t last long).

The first spacecraft to enter the atmosphere of Venus was the Soviet Venera 3 probe, which crash landed on March 1, 1966. It was destroyed in the upper atmosphere, so it wasn’t able to return any useful information back to Earth.

The next spacecraft to attempt a landing on Venus was the Soviet Venera 4 spacecraft, which entered the atmosphere on October 18, 1967. Venera 4 was able to deploy several science experiments and was operating them as it passed down through Venus’ atmosphere. But mission planners didn’t realize that the atmosphere of Venus was so thick, and so it ran out of battery power about 25 km above the surface of Venus. But this failure helped missions planners better understand conditions on Venus.

The Venera 7 spacecraft was built to handle 180 times Earth atmospheric pressure, and used a special parachute to drop it down quickly through the atmosphere. It’s believed that the parachute partially failed, and so it impacted the surface of Venus hard. It was only able to return temperature data back to Earth for about 20 minutes.

Venera 8 survived for 50 minutes on the surface of Venus, sending back data.

But the first photographs taken from the surface of Venus were sent back by the Venera 9 and 10 spacecraft. Venera 9 landed on the surface of Venus on October 22, 1975 and operated on the surface of Venus for 53 minutes. It sent back the first images ever captured from the surface of Venus. Venera 10 landed on October 25th, and captured images of pancake-shaped lava rocks. Venera 10 lasted for 65 minutes, and was able to see farther into the distance than Venera 9.

But the most successful Venus landings were the Soviet Venera 13 and 14, which touched down on March 1st and March 5th, 1982. They both survived for over an hour, and returned the first color images ever captured from the surface of Venus.

All of the spacecraft that ever landed on Venus are probably still there today.

If you’d like more information on Venus, check out Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

Reference:
NASA Solar System Exploration: Missions to Venus
NASA: Mission to Venus Timeline
NASA Planetary Science: Mission to Venus

August 4, 2009December 24, 2015 by Fraser Cain

Satellites of Venus

Artist's conception of Venus Express. Image credit: ESA

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Earth has the Moon, Mars has two moons, and even tiny Pluto has 3 satellites. So how many satellites does Venus have? Well, Venus has no natural satellites today. However, it’s possible that Venus did have natural satellites in the past.

Perhaps the biggest evidence that Venus once had a natural satellite is its current rotation. Seen from above, all the rest of the planets in the Solar System rotate counter-clockwise. That’s why eastern countries have an earlier sunrise than western countries. But the rotation of Venus is very slow and backwards. Seen from above, Venus rotates clockwise. In fact, a day on Venus lasts 243 Earth days, while a year on Venus lasts almost 225 days.

With this slow, backwards rotation, it’s possible that Venus experienced a catastrophic impact in its early history, just like the impact that created the Earth’s moon. While our Moon formed out at a stable point where it’s been slowly drifting away, it’s possible that a moon around Venus formed at an unstable distance and just crashed down into the planet.

It’s also possible that Venus captured an asteroid or two in the past, as astronomers believe happened with the Martian moons Phobos and Deimos. And this might also help us figure out what happened to satellites around Venus. Phobos is in an unstable orbit, and is expected to crash into Mars in the next 10 million years or so. So it’s possible that Venus had unstable moons orbiting it in the past, and they crashed into the surface. Venus is also much closer to the Sun than Earth, so the solar tides might just be too powerful to allow Mercury or Venus to have moons.

Unfortunately, the entire surface of Venus was resurfaced between 300-500 million years ago, and any evidence of crashing asteroids or moons has been covered up by volcanic flows. So perhaps we’ll never know if Venus ever had satellites.

Of course, Venus does have artificial satellites. At the time this article was written, ESA’s Venus Express was in orbit around Venus, capturing images and gathering data about our twin planet. And there could be more missions in the future.

If you’d like more information on Venus, check out Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

References:
NASA StarChild: The Planet Venus
NASA Solar System Exploration: Planet Venus

August 4, 2009December 24, 2015 by Fraser Cain

How Big is Venus?

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It’s been said that Venus is Earth’s twin planet, in terms of size and composition. So when you ask how big is Venus, you know it’s going to be pretty close to Earth. Of course, Venus has incredibly high temperatures, crushing pressure and a poisonous atmosphere, so it’s not exactly a twin of Earth.

Let’s start with the size of Venus. The diameter of Venus is 12,100 km. That’s about 95% of the diameter of Earth. If you put Earth and Venus side by side, it would be pretty hard to see which one was larger.

The volume of Venus is 9.38 x 10¹¹ km³, written out, that’s 938,000,000,000 cubic kilometers. Of course, since Venus isn’t as big as Earth, it actually has a smaller volume. Venus has only 86% the volume of Earth. In other words, you could fit 1.16 Venuses inside Earth.

The surface area of Venus is 4.6 x 10⁸ km². That works out to be 460,000,000 square kilometers. Again, that’s a little smaller than Earth. The surface area of Venus is only 90% the surface area of Earth.

If you’d like more information on Venus, check out Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

August 4, 2009December 24, 2015 by John Carl Villanueva

Center of the Universe

Where is the center of the Universe? One of the confusing aspects of the whole Big Bang idea is the notion that the Universe doesn’t have a center. You see, if we associate the Big Bang with just about any typical explosion, then we can be tempted to pinpoint the source of the explosion to be the center.

For example, if a firecracker explodes and we take a snapshot of it, then the outermost debris would mark the boundaries of the whole explosion. Looking at the directions of each debris, whether outermost or not, would give us an idea as to where the explosion first started and, subsequently, the center.

Furthermore, if there was a point of origin (the center) of the Big Bang similar to typical explosions, then that point and all regions near it would be comparatively warmer than all others. That is, as you move further from the center of a typical explosion, you would expect to measure cooler temperatures.

However, when scientists point their detectors to all directions, the readings they obtain indicate that the Universe, in general, is homogeneous. No large region is relatively warmer than the rest. Of course, each star is hotter than the regions away from it.

But if we look at many galaxies, and thus including the stars that comprise them, a homogeneous overall picture is painted. If that were so, then that center or point of origin of the explosion cannot exist.

The favorite analogy used by lecturers to simplify the concept of a universe having no center is that of the behavior of dots on the surface of an expanding balloon; for as we know, the Universe is expanding. If we imagine the dots to be galaxies, we can visualize the Universe’s expansion by observing how the dots are brought away from one another as air is slowly blown into the balloon.

For us to get a near accurate analogy, it is important that the observation be limited to the surface alone. If we try to interpret the expansion as being manifested by the whole balloon, we will be tempted into interpreting the geometric center of the balloon as the center of the expanding Universe.

Going back, if we just focus on the surface, you’ll notice that each and every dot will drift farther away from adjacent ones and that no single dot will appear as the center. Also, if you picture yourself as an ant at the center of a single dot, all the other dots will move away from you as if you were the center, just like in our universe.

We’ve got a few articles that touch on the center of the universe here in Universe Today. Here are two of them:

NASA also has some more:

Tired eyes? Let your ears help you learn for a change. Here are some episodes from Astronomy Cast that just might suit your taste:

Source: NASA Spitzer

August 4, 2009December 24, 2015 by Abby Cessna

Nine Planets

Planets in the Solar System. Image credit: NASA/JPL/IAU

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For seventy-six years, ever since Pluto was discovered in 1930, we had 9 planets in our Solar System. This all changed in 2006 when Pluto was demoted to the category of dwarf planets.

Mercury was only the second smallest planet back when there were 9. Mercury is closer to Earth than a number of other planets, but we cannot get a very good look at it because of its proximity to the Sun. Astronomers cannot use the Hubble Space Telescope to look at the planet because the Sun’s light would permanently damage the piece of equipment.

Venus is the brightest of all 9 planets. The only objects brighter in the Solar System are the Sun and the Moon. Venus is so bright that it can actually cast shadows. If the Moon is not out one night, you may be able to find some shadows thrown by the planet.

Earth is the densest of all planets in our Solar System. Our planet is composed mostly of iron, silicon, magnesium, and oxygen. Almost one-third of the planet (32.1%) is iron. There is nearly as much oxygen in the planet – 30.1%. There are lesser amounts of silicon (15.1%) and magnesium (13.9%). The materials are not spread equally throughout the planet. For example, most of the iron is in the core of the planet.

Ever since astronomers spotted what looked like canals on Mars, they have been searching for water and signs of life. While life has not been discovered yet, scientists have found deposits of water underneath the surface of the planet.

Not only is Jupiter the largest and most massive planet in our Solar System, but it is also the fastest spinning planet. Jupiter completes a full rotation in about 10 hours. The planet has actually flattened slightly at both ends due to the speed at which it spins.

Saturn does not have the most moons of any planet in our Solar System – that distinction goes to Jupiter with 63 moons – but Saturn comes in a close second with 60 moons. When Galileo first saw Saturn with a telescope, he thought that the planet’s rings were moons. Astronomers were not able to determine what the rings were until they developed better telescopes.

Uranus is the only planet to rotate on its side. This planet has the greatest axial tilt of any planet in our Solar System – 98°. As a result of this extreme tilt, the north pole is in darkness for 42 years then it gets 42 years of light before repeating the cycle.

Neptune is quite a bit larger than Earth, but its gravity is very similar. If you could stand on Neptune – you cannot because it does not actually have a surface – then you would only experience approximately 17% more gravity than you would standing on Earth.

Pluto, which was discovered in 1930, was the ninth planet. Pluto was by far the smallest planet. In fact, Pluto is even smaller than the Earth’s moon. This tiny planet was also the coldest one. Although its temperatures can drop to -240°C, the average temperatures on Pluto are -219°C.

Universe Today has articles on all 9 planets of the solar system including list of the planets and planets in the Solar System.

If you’d like more info on the nine planets, check out NASA’s Solar System exploration page, and here’s a link to NASA’s Solar System Simulator.

Astronomy Cast has episodes on all the 9 planets of the Solar System including Mercury.