{"id":42876,"date":"2023-03-16T08:53:01","date_gmt":"2023-03-16T08:53:01","guid":{"rendered":"https:\/\/www.skyatnightmagazine.com\/?p=117112"},"modified":"2023-03-16T09:32:33","modified_gmt":"2023-03-16T09:32:33","slug":"4-mistakes-astronomers-made-about-our-solar-system","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/4-mistakes-astronomers-made-about-our-solar-system\/","title":{"rendered":"4 mistakes astronomers made about our Solar System"},"content":{"rendered":"

Even astronomers make mistakes! Patrick Moore considers some of the biggest blunders made about the Solar System, including one of his own. <\/p>

By Patrick Moore\n \t\t<\/p>

Published: Thursday, 16 March 2023 at 12:00 am<\/p>

\n\n

A<\/span>stronomers are not infallible. We make mistakes, but unlike politicians we\u2019re honest enough to admit them.<\/p>\n

The classic case, to my mind, goes back over 10 years now, when radio astronomers at Jodrell Bank believed that they had located a planet in orbit round a pulsar<\/a>.<\/p>\n

In fact, they had made an elementary mistake in their calculations.<\/p>\n

It would have been so easy to blame a computer fault or something of the kind.<\/p>\n

Not a bit of it. Jodrell Bank\u2019s director, Andrew Lyne, said simply, \u201cWe got it wrong.\u201d<\/p>\n

His frankness further enhanced his already worldwide reputation.<\/p>\n

Casting my mind back, I can think of three cases where almost everyone got it wrong.<\/p>\n

Flora on Mars<\/strong><\/h2>\n
\"""\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Drawings of Mars, its \u2018canals\u2019 and polar ice caps, from observations made at the Lowell Observatory, Flagstaff, Arizona, US, 8-12 July, 1907. Photo by Ann Ronan Pictures\/Print Collector\/Getty Images<\/span><\/figcaption><\/div>\n

By the end of the Second World War, Percival Lowell\u2019s canal-building Martian engineers had been reluctantly consigned to the realm of science fiction, but it was still believed that the dark areas were tracts of primitive vegetation.<\/p>\n

In 1956 G\u00e9rard de Vaucouleurs, one of the leading planetary observers, claimed that when water vapour was released from the Martian polar ice caps, every spring, a \u201cwave of darkening\u201d spread slowly towards the equator, as the vegetation was revived by the arrival of moisture.<\/p>\n

Even the canals had \u201ca basis of reality\u201d.<\/p>\n

One comment, made by the Estonian astronomer Ernst \u00d6pik, was particularly persuasive. As we know, Mars experiences frequent dust storms<\/a> and some of these are global.<\/p>\n

I remember when Mariner 9<\/a> was approaching the planet and I was asked by NASA to go and make some observations with the Innes 26-inch refractor at Johannesburg.<\/p>\n

On my first view, I saw a virtually blank disc \u2013 I likened it to a red Venus. It took weeks for the dust to clear.<\/p>\n

\"""\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Two images captured by the Mars Orbiter Camera on NASA\u2019s Mars Global Surveyor orbiter in 2001 show a change in the planet\u2019s appearance as a result of haze raised by dust storms. These images were taken about a month apart. Did early astronomers believe this to be growing vegetation? Credit: NASA\/JPL-Caltech\/MSSS<\/span><\/figcaption><\/div>\n

Well, said \u00d6pik, if the dust covers the entire planet, the dark regions must be made\nof plants that can grow and push the dust away, otherwise the surface would stay red all the time.<\/p>\n

Most agreed. It was only when close-range pictures were obtained that the vegetation theory had to be abandoned.<\/p>\n

As for the wave of darkening \u2013 well, I could see no sign of it, even though I\u2019d been making regular observations.<\/p>\n

I was right; others were not. In a moment I\u2019ll come to a controversy in which I was badly wrong but first, let\u2019s consider Venus<\/p>\n

Venus\u2019s rotational period<\/strong><\/h2>\n
\"""\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Credit: NASA\/JPL-Caltech<\/span><\/figcaption><\/div>\n

Venus<\/a> had been regarded as \u2018the planet of mystery\u2019. In size and mass it is almost a twin of Earth and it is the brightest object in our sky, apart from the Sun<\/a> and the Moon.<\/p>\n

But Venus\u2019s surface lies below its cloudy, obscuring atmosphere.<\/p>\n

The orbital period was 224.7 days but what about the axial rotation period \u2013 Venus\u2019s \u2018day\u2019? Nobody knew.<\/p>\n

Efforts were made to measure it by following the drifting of surface features across the disc.<\/p>\n

This is easy enough with Mars<\/a> or Jupiter<\/a> but the markings on Venus were too vague and impermanent to yield any reliable results.<\/p>\n

Estimates ranged from around 24 hours up to 224.7 days.<\/p>\n

If the latter had been correct, Venus would have a \u2018captured\u2019 or \u2018synchronous\u2019 rotation, keeping the same face turned permanently sunward just as the Moon behaves with respect to Earth (which is why we always see the same side of the Moon<\/a>).<\/p>\n

\"""\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
A view of Venus captured by the Mariner 10 probe. Credit: NASA\/JPL-Caltech<\/span><\/figcaption><\/div>\n

The general feeling was that the period was likely to be \u2018a few weeks\u2019, following the photographic results of work by GP Kuiper.<\/p>\n

In 1960 I wrote a small book about Venus. In it were listed the rotation periods given by different authorities.<\/p>\n

There were over 100 estimates and every one of them turned out to be wrong.<\/p>\n

The true period of Venus\u2019s rotation is 243 days, which is longer than the orbital period \u2013 and even more confusingly, Venus spins backwards<\/a>, from east to west, opposite to that of Earth and Mars.<\/p>\n

To an observer on the surface, the Sun would rise in the west and set in the east, though of course it could never be clearly seen through the clouds.<\/p>\n

There is no such thing as a sunny day on our sister world.<\/p>\n

Venus is covered with water<\/strong><\/h2>\n
\"""\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Venus\u2019s northern hemisphere, as seen by NASA\u2019s Magellan probe. Credit: NASA\/JPL<\/span><\/figcaption><\/div>\n

Venus is known today to be a scorching-hot world, with lava flows together with volcanoes that may well be active.<\/p>\n

But a few decades ago there was wide support for the picture painted by FI Whipple and DH Menzel, according to whom Venus was almost completely covered with water.<\/p>\n

An oceanic Venus sounded attractive.<\/p>\n

Life could begin there and evolve just as it presumably did in our seas long ago, so that our first astronauts might be welcomed by an ichthyosaurus or perhaps a pterodactyl.<\/p>\n

The Moon\u2019s craters are volcanic<\/strong><\/h2>\n
\"""\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
The Moon\u2019s limb, imaged by the Apollo 10 astronauts in 1969. Credit: NASA\/ISC<\/span><\/figcaption><\/div>\n

Now for the Moon. Originally it was assumed that the craters were of volcanic origin, because they looked like volcanic calderae and there seemed to be no obvious alternative.<\/p>\n

A suggestion made in the 1830s by Franz von Paula Gruithuisen that they could be due to falling meteorites was not taken very seriously.<\/p>\n

However, after the end of the Second World War the impact theory was revived, initially by Ralph Baldwin in America and this time it took root.<\/p>\n

At times the discussions between the \u2018volcanists\u2019 and the \u2018meteoricists\u2019 became strangely heated.<\/p>\n

I was a convinced volcanist and I put forward my arguments, which I firmly believed to be conclusive.<\/p>\n

For instance, when one crater breaks into another, it is the smaller formation that intrudes into the larger.<\/p>\n

This is true in 99.9% of cases, so that the crater distribution is not random, as it would be following a meteoritic bombardment.<\/p>\n

\"""\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Crater Petavius. Credit: Pete Lawrence<\/span><\/figcaption><\/div>\n

Similarly, large structures of obviously different ages are lined up in chains, for example: Petavius<\/a>; Langrenus; Vendelinus.<\/p>\n

And when one crater breaks into another, the wall of the broken crater can often remain undamaged right up to the point of junction.<\/p>\n

There are endless examples of the non-random distribution of the craters.<\/p>\n

Many rounded peaks have summit craterlets, symmetrically placed twins (Challis\/Main), concentric craters (Taruntius); crater valleys (Rheita)\u2026 But why go on?<\/p>\n

Finally, if the Moon has been so pelted and considering that there is no atmospheric erosion, where have all the meteorites gone?<\/p>\n

Certainly they are not lying around waiting to be picked up, as in Antarctica.<\/p>\n

I think I was one of the last of the volcanists to admit defeat but in the end I had no choice.<\/p>\n

There has undoubtedly been widespread volcanism on the Moon but the craters are not calderae, as I thought.<\/p>\n

To the impact theory \u2013 sorry. This was one of my major blunders!<\/p>\n

This article originally appeared in the July 2007 issue of <\/strong><\/em>BBC Sky at Night Magazine<\/strong>.<\/strong><\/em><\/p> <\/body><\/html>\n

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