Venus Archives

December 29, 2009December 24, 2015 by Nancy Atkinson

Where To Next for NASA’s Solar System Exploration?

From top to bottom, pictured are the moon, Venus, and an asteroid.From top to bottom, pictured (not to scale) are the moon, Venus, and an asteroid. These three celestial bodies from our solar system are possible candidates for NASA's next space venture.

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Where is NASA going next to probe our solar system? The space agency announced today they have selected three proposals as candidates for the agency’s next space venture to another celestial body in our solar system. The proposed missions would probe the atmosphere composition and crust of Venus; return a piece of a near-Earth asteroid for analysis; or drop a robotic lander into a basin at the moon’s south pole to return lunar rocks back to Earth for study. All three sound exciting!

Here are the finalists:

Surface and Atmosphere Geochemical Explorer, or SAGE, mission to Venus would release a probe to descend through the planet’s atmosphere. During descent, instruments would conduct extensive measurements of the atmosphere’s composition and obtain meteorological data. The probe then would land on the surface of Venus, where its abrading tool would expose both a weathered and a pristine surface area to measure its composition and mineralogy. Scientists hope to understand the origin of Venus and why it is so different from Earth. Larry Esposito of the University of Colorado in Boulder, is the principal investigator.

Origins Spectral Interpretation Resource Identification Security Regolith Explorer spacecraft, called Osiris-Rex, would rendezvous and orbit a primitive asteroid. After extensive measurements, instruments would collect more than two ounces of material from the asteriod’s surface for return to Earth. The returned samples would help scientists better undertand and answer long-held questions about the formation of our solar system and the origin of complex molecules necessary for life. Michael Drake, of the University of Arizona in Tucson, is the principal investigator.

MoonRise: Lunar South Pole-Aitken Basin Sample Return Mission would place a lander in a broad basin near the moon’s south pole and return approximately two pounds of lunar materials for study. This region of the lunar surface is believed to harbor rocks excavated from the moon’s mantle. The samples would provide new insight into the early history of the Earth-moon system. Bradley Jolliff, of Washington University in St. Louis, is the principal investigator.

The final project will be selected in mid-2011, and for now, the three finalists will receive approximately $3.3 million in 2010 to conduct a 12-month mission concept study that focuses on implementation feasibility, cost, management and technical plans. Studies also will include plans for educational outreach and small business opportunities.

The selected mission must be ready for launch no later than Dec. 30, 2018. Mission cost, excluding the launch vehicle, is limited to $650 million.

“These are projects that inspire and excite young scientists, engineers and the public,” said Ed Weiler, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. “These three proposals provide the best science value among eight submitted to NASA this year.”

The final selection will become the third mission in the program. New Horizons, launched in 2006, will fly by the Pluto-Charon system in 2015 then target another Kuiper Belt object for study. The second mission, called Juno, is designed to orbit Jupiter from pole to pole for the first time, conducting an in-depth study of the giant planet’s atmosphere and interior. It is slated for launch in August 2011.

Visit the New Frontiers program site for more information.

September 3, 2009April 26, 2016 by Ian O'Neill

UFOs, a Green Venus and Sun Gobbling? Isn’t That Going a Little Far, Mrs Hatoyama?

[/caption]“While my body was asleep, I think my soul rode on a triangular-shaped UFO and went to Venus.”

This might sound like a quote taken from the ramblings of a conspiracy theorist or the chant from someone who spent an hour too many at an Amsterdam coffee shop, but it wasn’t.

Actually, these are the words of the wife of the Japanese premier-in-waiting Yukio Hatoyama.

Mrs Miyuki Hatoyama might be married to a man Japan nicknames “The Alien,” but it looks like it’s not him who has dreams of an extraterrestrial nature…

If there’s one thing politicians must dread when they are voted into a position of power, it’s the past. Previous indiscretions, past conversations, old business that involved major campaign donors; all of these must keep many government ministers awake at night, worried that the media will dig up some dirt.

However, in the case of the soon-to-be prime minister of Japan (who won the recent elections with a landslide victory), it’s his 66-year old wife who wrote something last year in a book called Very Strange Things I’ve Encountered, that’s causing a stir. But through his wife’s own admission, Yukio Hatoyama is an open minded fellow and probably won’t be concerned about what the public may think of Miyuki’s book.

Very Strange Things documents Mrs Hatoyama’s experiences 20 years ago when a UFO picked her up and took her to Venus. “It was a very beautiful place and it was really green,” she observed.

If by “green” she actually means “dark brown,” and by “beautiful” she means “a tropical, bone crushing atmosphere, stuffed with poisonous gas and a landscape resembling hell,” then I think Miyuki really did fly there.

Naturally, after she had her joyride to Venus, Miyuki arrived back in bed, next to her now ex-husband who told her it was just a dream.

In addition to her night-time jaunts around the Solar System, Miyuki also partakes in a little solar feast every now and again. On a Japanese TV show earlier this year, Miyuki went into some detail about her spiritualistic beliefs.

“I also eat the sun,” she said on the program, closing her eyes, pulling pieces off an imaginary Sun. “Like this, hum, hum, hum. It gives me enormous energy […] My husband has recently started doing that too.”

This all seems like a lot of fun, but what does this mean for Japan? As noted by Keith Cowing over at NASA Watch, perhaps we’ll see a boost in JAXA (the Japanese space agency) funding. It might also go some way to explaining why there’s been a surge of interest in Japanese space solar power!

Things might go a little too far if we start seeing JAXA UFO patrols in low-Earth orbit, but for now, I suspect it’s going to be a rather flamboyant term in office for the Hatoyama’s…

Sources: Reuters, NASA Watch, Time

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.

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.

Reference:
NASA Solar System Exploration: Venus

July 14, 2009December 24, 2015 by Nancy Atkinson

New Map Hints at Venus’ Wet, Volcanic Past

Artistic interpretation of a possible volcano on Venus. Credits: ESA - AOES Medialab

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Venus is often referred to as Earth’s twin, as the two planets share a similar size. But perhaps the similarities don’t end there. A new infrared map from Venus Express hints that our neighboring world may once have been more Earth-like, with a plate tectonics system and an ocean of water. While previous radar images have given us a glimpse of Venus’ cloud-shrouded surface, this is the first map that hints at the chemical composition of the rocks. The new data are consistent with suspicions that the highland plateaus of Venus are ancient continents, once surrounded by ocean and produced by past volcanic activity.

“This is not proof, but it is consistent. All we can really say at the moment is that the plateau rocks look different from elsewhere,” says Nils Müller at the Joint Planetary Interior Physics Research Group of the University Münster and DLR Berlin, who headed the mapping efforts.

The first temperature map of the planet's southern hemisphere at infrared wavelengths, charted with Venus Express's Visible and Infrared Thermal Imaging Spectrometer, VIRTIS. Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

The map shows Venus’ southern hemisphere comprised over a thousand individual images, recorded between May 2006 and December 2007. The Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument captured infrared radiation given off by the various surfaces on Venus during the spacecraft’s night-time orbits around the planet’s southern hemisphere.

Different types of rocks radiate different amounts of heat at infrared wavelengths owing to a material characteristic known as emissivity. The new map shows that the rocks on the Phoebe and Alpha Regio plateaus are lighter in color and look old compared to the majority of the planet. On Earth, such light-colored rocks are usually granite and form continents.

“If there is granite on Venus, there must have been an ocean and plate tectonics in the past,” says Müller.
Granite is formed when ancient rocks, made of basalt, are driven down into the planet by shifting continents, a process known as plate tectonics. The water combines with the basalt to form granite and the mixture is reborn through volcanic eruptions.

Müller points out that the only way to know for sure whether the highland plateaus are continents is to send a lander there. Over time, Venus’ water has been lost to space, but there might still be volcanic activity. The infrared observations are very sensitive to temperature. But in all images they saw variations of only 3–20°C, instead of the kind of temperature difference they would expect from active lava flows.

“Venus is a big planet, being heated by radioactive elements in its interior. It should have as much volcanic activity as Earth,” he says. Indeed, some areas do appear to be composed of darker rock, which hints at relatively recent volcanic flows.

Lead image caption: Artistic interpretation of a possible volcano on Venus. Credits: ESA – AOES Medialab

Source: ESA

March 13, 2009December 24, 2015 by Anne Minard

Earth Cyclones, Venus Vortices Have Much in Common

Scientists have spotted an S-shaped feature in the center of the vortices on Venus that looks familiar — because they’ve seen it in tropical cyclones on Earth.

Researchers from the United States and Europe spotted the feature using NASA’s Pioneer Venus Orbiter and The European Space Agency’s Venus Express. Their new discovery confirms that massive, swirling wind patterns have much in common where they have been found — on Venus, Saturn and Earth.

At cloud top level, Venus’ entire atmosphere circles the planet in just about four Earth days, much faster than the solid planet does. Despite this “superrotation,” some dynamical and morphological similarities exist between the vortex organization in the atmospheres of Venus’s northern and southern hemispheres and tropical cyclones and hurricanes on Earth.

Organization of the Venus atmospheric circulation into two circumpolar vortices, one centered on each pole, was first deduced more than 30 years ago from Mariner 10 ultraviolet images. The S-shaped feature in the center of the vortices on Venus was first detected by the Pioneer Venus Orbiter near the northern pole and recently by Venus Express orbiter around the southern pole. It is also known to occur in Earth’s tropical cyclones.

Using an idealized nonlinear and nondivergent barotropic model, lead author Sanjay S. Limaye, of the University of Wisconsin-Madison, and his colleagues are proposing that these S-shaped features are the manifestations of barotropic instability. The feature can be simulated with a barotropic model and, like in the vortices on Venus and in tropical cyclones, it is found to be transient.

Another similarity between the observed features in the vortex circulations of Venus and in terrestrial hurricanes is the presence of transverse waves extending radially outward from the vortex centres. The lack of observations of such features in Earth’s polar vortices is suggestive that the dynamics of the Venus polar vortices may have more in common with hurricanes than their more direct terrestrial counterparts.

Given the challenges in measuring the deep circulation of Venus’s atmosphere, the authors expect that the morphological similarities between vortices on Earth and Venus might help scientists better understand atmospheric superrotation on Venus and guide future observations.

IMAGE CAPTIONS: 1. The ‘eye of the hurricane’ on Venus, taken by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on board Venus Express. The yellow dot represents the south pole. Credit: ESA 2. An infrared satellite image of Hurricane Howard [1998], showing an S-shaped pattern in the low (warm) clouds in the tropical cyclone’s eye. Credit: Sanjay S. Limaye.

Source: Geophysical Research Letters

February 24, 2009December 24, 2015 by Nancy Atkinson

Venus is Glowing in the Dark!

A false-colour composite image of Venus’s atmosphere was obtained by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on board ESA’s Venus Express, from a limb (or profile) perspective.

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Venus is glowing in infrared! At least at night, anyway. The Venus Express spacecraft has observed an eerie glow in the night-time atmosphere of Venus. This infrared glow comes from nitric oxide and is showing scientists that the atmosphere of Earth’s nearest neighbor is a temperamental place of high winds and turbulence. Since this glow is infrared, we can’t see it with our eyes but lucky for us, the ESA’s spacecraft is equipped with the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument, which can see these wavelengths. A glow like this has never been detected in the atmospheres of Earth or Mars, even though nitric oxide molecules are present. So just why is Venus glowing, and what is this glow telling us?

“The nightglow can give us a lot of information,” says Antonio García Muñoz, who was at the Australian National University when the research was carried out; he is now located at the Instituto de Astrofísica de Canarias, Tenerife, Spain. “It can provide details about the temperature, wind direction, composition and chemistry of an atmosphere.”

VIRTIS has made two clear-cut detections of the so-called nightglow for nitric oxide at Venus. This is the first time such infrared detections have been made for any planet and provide a new insight into Venus’s atmosphere

The nightglow is ultimately caused by the Sun’s ultraviolet light, which streams into a planet’s atmosphere and breaks the molecules up into atoms and other simpler molecules. The free atoms may recombine again and, in specific cases, the resulting molecule is endowed with some extra energy that is subsequently lost in the form of light. On the day-side of the planet, any atoms that do find their way back together are outshone by the sunlight falling into the atmosphere.

But on the night-side, where atoms are transported by a vigorous diurnal circulation, the glow can be seen with appropriate instruments, such as VIRTIS.

It also highlights a new mystery. “These results show that there could be at least twice as much hydrogen in the upper atmosphere of Venus than we thought,” says Delva. The detected hydrogen ions could exist in atmospheric regions high above the surface of the planet; but the source of these regions is unknown.

Artist's impression shows Venus Express focussing on studying the peculiar atmosphere of Venus,

The nightglow on Venus has been seen at infrared wavelengths before, betraying oxygen molecules and the hydroxyl radical, but this is the first detection of nitric oxide at those wavelengths. It offers data about the atmosphere of Venus that lies above the cloud tops at around 70 km. The oxygen and hydroxyl emissions come from 90-100 km, whereas the nitric oxide comes from 110-120 km altitude.

Yet, even VIRTIS cannot see the nitric oxide nightglow all the time because it is often just too faint. “Luckily for us, Venus has a temperamental atmosphere,” says García Muñoz, “Packets of oxygen and nitrogen atoms are blown around.” Sometimes these become dense enough to boost the brightness of the nightglow, making it visible to VIRTIS.

Venus Express can observe the three nightglow emissions simultaneously, and this gives rise to a mystery. The nightglows from the different molecules do not necessarily happen together. “Perhaps when we have more observations, we will understand the correlation between them,” says García Muñoz.

In order to do that, the VIRTIS team plans to continue monitoring the planet, building up a database of this fascinating phenomenon.

Source: ESA

January 15, 2009December 24, 2015 by Nancy Atkinson

Venus Possibly Had Continents, Oceans

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A new look at data gathered from the Galileo spacecraft in 1990 reveals that Venus at one time may have been habitable, with evidence of past continents and oceans. In a flyby of Venus on the spacecraft’s journey to Jupiter, a near-infrared mapping instrument detected signatures which the researchers have interpreted as granite. An international team led by planetary scientist George Hashimoto, at Okayama University, Japan, found that Venus’s highland regions emitted less infrared radiation than its lowlands. One interpretation of this dichotomy, says the team’s new paper, is that the highlands are composed largely of ‘felsic’ rocks, particularly granite. Granite, which on Earth is found in continental crust, requires water for its formation.

The Galileo spacecraft was the first use of infrared to look at Venus. Scientists had believed that only radar could see through the dense clouds of sulfuric acid in Venus’s atmosphere to the surface. “Detecting the surface in the infrared is a breakthrough,” co-author Kevin Baines from JPL was quoted in an article in Nature.

The article also quoted another JPL scientist, David Crisp, who was not involved in this study as saying these new conclusions aren’t supported either by the available data or the team’s own models.

“We understand our paper doesn’t resolve everything,” responds co-author Seiji Sugita, a planetary scientist at the University of Tokyo. Sugita says the next step is to apply their models to data from the European Space Agency’s Venus Express spacecraft, which is already orbiting Venus, and the Japanese Space Agency’s Venus Climate Orbiter, scheduled for launch in 2010.

The possible presence of granite suggests that tectonic plate movement and continent formation may have occurred on Venus, as well as recycling of water and carbon between the planet’s mantle and atmosphere.
Venus is now hellishly hot and dry, with an atmosphere of 96% carbon dioxide and a surface temperature of around 460 degrees C, but some scientists think our neighboring planet may have once have been more like Earth.

Another scientist quoted in the Nature article, geophysicist Norm Sleep of Stanford University in California said Venus might have once been almost entirely underwater. “Although without further geochemical data, he adds, we don’t know whether this early ocean’s temperature was 30 degrees C or 150 degrees C,” he said.

But any ocean on Venus would have lasted only a few hundred million years. As the Sun became hotter and brighter, the planet experienced a runaway greenhouse effect. “Any life on Venus that hadn’t figured out how to colonize the cloud tops a billion years after the planet’s formation would have been in big trouble,” says Sleep.

Sources: Nature, Abstract

December 18, 2008December 24, 2015 by Fraser Cain

How Hot is 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

You might be surprised to know that Venus is the hottest planet in the Solar System. The temperature across the entire planet is 735 Kelvin, or 462 degrees Celsius.

That makes it hotter than Mercury, which can dip down to -220 degrees Celsius and get up to 420 degrees C. Venus is nearly twice as far away from the Sun as Mercury, and receives 25% of it’s sunlight.

The temperature on the surface of Venus is the same across the entire planet. It doesn’t matter if it’s day or night, at the poles or at the equator – the temperature is always the same 462 degrees.

[/caption]So why is Venus so hot? Billions of years ago, the atmosphere of Venus was probably very similar to the Earth’s, with liquid water lasting on the surface. But a runaway greenhouse effect evaporated all the water, leaving a thick atmosphere of carbon dioxide. The light from the Sun is trapped by the carbon dioxide atmosphere and keeps the planet so warm.

It’s also believed that Venus once had plate tectonics like we have on Earth. Here on Earth, the plate tectonics help regulate the amount of carbon dioxide in the atmosphere by trapping excess carbon dioxide underneath the surface of the Earth. When the plate tectonics stopped, the carbon cycle stopped as well, and carbon dioxide was able to accumulate in the atmosphere of Venus.

Want to learn about other planets in the Solar System? Here’s how hot Mercury can get, and here’s an article about the hottest place on Earth.

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

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

December 3, 2008December 24, 2015 by Nancy Atkinson

Seeing Venus in a New Light

Venus in ultraviolet. Credits: ESA/MPS/DLR/IDA

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New images taken by instruments on board ESA’s Venus Express are providing insight into the turbulent atmosphere of our neighboring planet. When viewed in beyond visible light, the ultraviolet reveals the structure of the clouds and the dynamic conditions in the atmosphere of Venus, where the infrared provides information on the temperature and altitude of the cloud tops. Most intriguing are the puzzling dark and bright zones seen on Venus in ultraviolet.

Scientists have seen equatorial areas on Venus that appear dark in ultraviolet light, and have been mystified by them. The new views with Venus Express show the cause of these different colored areas is the uneven distribution of a mysterious chemical in the atmosphere that absorbs ultraviolet light, creating the bright and dark zones. While the scientists haven’t been able to identify the chemical, they have figured out the process that causes the changes in cloud types across Venus.

Professor Fred Taylor, one of the Venus Express scientists, from Oxford University said, “The features seen on Venus in ultraviolet light have been a puzzle to astronomers for nearly a century. These new images have revealed the structure in the clouds that produces them and shows how they result from complex meteorological behaviour. We can now study in much greater detail and try to understand the origin of features such as the large hurricane-like vortex over the north and south poles. Like many things on Venus, including global warming, this feature has similarities to atmospheric and environmental process on Earth, but the Venus version is much more extreme.”

With data from Venus Express, scientists have learned that the equatorial areas on Venus that appear dark in ultraviolet light are regions of relatively high temperature, where intense convection brings up dark material from below. In contrast, the bright regions at mid-latitudes are areas where the temperature in the atmosphere decreases with depth.

Venus in infrared and ultraviolet. Credits: VMC ultraviolet image: ESA/MPS/DLR/IDA VIRTIS infrared image: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

Observations in the infrared have been used to map the altitude of the cloud tops. Researchers were surprised to find the clouds in both the dark tropics and the bright mid-latitudes are located at about the same height of about 72 km.

Sources: ESA, Science & Technology Facilities Council

October 10, 2008December 24, 2015 by Ian O'Neill

Why is Venus Express Looking for Life on Earth?

Earth atmospheric molecules detected by Venus Express (ESA)

[/caption]If you are an astronomer looking for a habitable exoplanet orbiting a far-off star, what do you look for? We know from personal experience that we need oxygen and water to live on Earth, so this is a good place to start; look for exoplanets with the spectroscopic signature of O₂ and H₂O. But this isn’t enough. Venus has oxygen and water in its atmosphere too, so if we only used these two indicators as a measure for habitability, we would be sorely disappointed to find a water and oxygen-rich Venus-like world which has little chance of supporting life (as we know it).

In an effort to understand what a “habitable planet” looks like from afar, European Space Agency (ESA) scientists have decided to do a bit of retrospective astronomy. Venus Express, currently in orbit around Venus, is being used to look back at the blue dot we call home to help us understand what a real habitable planet looks like…

Venus Express (sister ship of ESA’s Mars Express) was launched in November 2005 to begin its seven month journey to Venus. As the spacecraft left Earth orbit, it turned around to take a picture of the blue globe with its Visible and Infrared Thermal Imaging Spectrometer (VIRTIS), but the significance of this quick observation wasn’t realised until a year after Venus Express had entered Venusian orbit. Could the robotic craft be used to watch the Earth from afar?

Giuseppe Piccioni, Venus Express VIRTIS Co-Principal Investigator, in Italy, has been heading a sustained campaign of Earth observations using the VIRTIS instrument orbiting a planet 0.3 AU closer to the Sun. Although Venus has often been referred to as “Earth’s sister planet” the difference couldn’t be more stark. With atmospheric pressures some hundred times that of the Earth, with a choking cocktail of poisonous gases and high surface temperatures, Venus is hardly conducive for life. Earth, on the other hand, has a bountiful ecosystem where life has thrived for over three billion years. However, Piccioni is aware that if viewed from a distance, both Earth and Venus contain some of the basic ingredients for life; how can we be sure distant exoplanets are more Earth-like or more Venus-like? After all, planet habitability doesn’t seem to depend on just oxygen and water.

“We see water and molecular oxygen in Earth’s atmosphere, but Venus also shows these signatures. So looking at these molecules is not enough,” says Piccioni. So, in an attempt to seek out other forms of life, the Italian astronomer is looking toward Earth to pick out more subtle signals for the presence of life on alien worlds.

Earth’s oxygen and water as detected by Venus Express (ESA) — Earth’s oxygen and water as detected by Venus Express. The simulated images of Earth are to show which side of the planet was facing Venus at the time; in actuality Earth would appear as a one-pixel dot (ESA)

Venus Express can observe Earth about three times a month, and over the last two years, VIRTIS has captured 40 terrestrial images for analysis. The light captured from these Earth observations cover spectral wavelengths from visible through to near-infrared, but when viewed from Venus, the Earth appears only as a small dot, no bigger than a single pixel in Venus Express’ cameras. Far from being a hindrance, this small dot will help future exoplanet hunters.

Although there are no surface features, this small dot still holds a lot of information. By splitting the light observed into its component wavelengths, the composition of the terrestrial atmosphere can be analysed. Therefore, spectroscopic signals from plant life could be detected for example. “Green plants are bright in the near infrared,” said David Grinspoon, a Venus Express Interdisciplinary Scientist from the Denver Museum of Nature & Science, Colorado, who suggested the programme of sustained Earth observation. “We want to know what can we discern about the Earth’s habitability based on such observations. Whatever we learn about Earth, we can then apply to the study of other worlds,” he added.

Exoplanet hunters are finding more and more alien worlds orbiting stars many light years away, it is only a matter of time before we have the technological ability to image the one-pixel spot of an Earth-like world. By understanding how our habitable planet looks from Venus, we can begin to understand whether these exoplanets are indeed “Earth-like” in every sense of the word…

Source: ESA

Here’s an article about the famous blue dot image of Earth.