Being 2nd rock from sun took toll
Venus became the solar system’s baking hellhole by making a classic real estate mistake: building in the wrong neighborhood, according to research released Wednesday presenting the first comprehensive findings from Europe’s Venus Express spacecraft.
Instruments aboard the craft, which has been orbiting the haze-shrouded planet for almost 20 months, show that Venus and Earth are not just sister planets, but are nearly twins in important ways.
They are comparable in size and mass, have similar amounts of carbon dioxide and once probably possessed nearly equal amounts of water.
But while Earth matured into the solar system’s beauty queen, replete with forests, rivers and oceans, Venus, about 30% closer to the sun, lost nearly all its water. Its clouds today are filled with sulfuric acid.
The reason? Location, location, location.
“It’s a sobering little tale,” said Andrew Ingersoll, an astronomer at Caltech in Pasadena, who wrote one of the nine research articles published in the current issue of the journal Nature. “Venus is just too close to the sun.”
Much of this was known, or suspected, about the planet before the European Space Agency launched Venus Express in November 2005. It’s the 30th spacecraft to visit the solar system’s second planet from the sun, beginning with NASA’s Mariner 2 mission in 1962.
The craft is the first European mission to Earth’s closest planetary neighbor, and the first of any kind to tour Venus in a decade.
With a suite of modern instruments, including spectrometers and imagers capable of piercing the thick clouds down to the planet’s surface, the 1,300-pound spacecraft is probing Venus’ poisonous atmosphere in unprecedented detail.
“They’ve made some progress on questions that have been around for a while,” Ingersoll said.
Specifically, Venus Express was able to confirm a much-debated measurement by the Pioneer mission in 1978, which found large amounts of deuterium -- a heavier isotope of hydrogen -- in the atmosphere.
This is consistent with a massive loss of hydrogen to space, Ingersoll said. The mechanism probably involved intense radiation from the sun, 67 million miles away, breaking the enormous quantities of water vapor in the atmosphere into its constituents of hydrogen and oxygen.
The hydrogen then escaped to space, while the oxygen and deuterium, along with carbon dioxide, stuck around, heating the atmosphere and making the surface, at about 870 degrees Fahrenheit, hotter than the innermost planet, Mercury.
The abundance of carbon dioxide has created a crushing surface pressure equal to what is experienced in a diving bell a mile under the sea on Earth.
“This is the opposite of a benign environment,” Ingersoll said.
A visitor to Venus from Los Angeles, if properly protected, might not feel too ill at ease. The haze would resemble a smoggy day in summer. “Except the smog in Los Angeles is not made of sulfuric acid,” Ingersoll said.
Unlike Mars, which is believed to have once featured standing lakes and possibly even shallow seas, Venus probably never had an ocean, Ingersoll said.
Besides losing all its water to space, another key difference between Venus and Earth is that on Venus, the carbon dioxide is floating in the atmosphere. On Earth, it’s mostly locked up in limestone deposits.
This is one reason the runaway greenhouse effect that occurred on Venus has not happened on Earth.
Some environmentalists point to Venus as an example of what could happen on Earth unless governments take action to halt global warming. But Ingersoll said Earth was unlikely to go down the Venusian path, at least for the foreseeable future.
“Over the next century, we may get a 1% increase in heating,” Ingersoll said. “Venus has had a 30% increase in heating. In the next 100 years we will have some problems, but they won’t be as drastic as turning the Earth into Venus.”
Though Venus Express has been able to answer some questions about Earth’s closest sibling, mysteries remain. The spacecraft found telltale evidence of lightning. Lightning has been observed on other planets, but Venus’ clouds are too thin to produce lightning, at least by Earth’s model.
“So it’s a mystery,” Ingersoll said.
“I think mysteries are good. They cause you to examine your experience and biases.”