Mars

[Guest guest]

Dear Jay,

 

The article you forwarded is not very accurate. The closest Mars was to the

earth was actually 2 years ago in Agust 2003. We watched Mars athen through

my husband's telescope and it was beautiful, but no where near the size of

the full moon at 75x magnification.. Here's an article from Sky and Telscope

2003 which gives the real, accurate info:.

 

best wishes,

Willa

 

Mars Record for the Ages

By Roger W. Sinnott

 

 

The red planet as seen by Mars Global Surveyor in

June 2001, just before the start of a globe-girdling dust storm that hid

most surface details from view (click for before-and-after comparison).

Courtesy NASA/JPL/Malin Space Science Systems.

 

 

 

 

This is a special year for Mars. Already the planet is shining big and

bright in the southeastern sky before dawn, and it's drawing closer to us

week by week. For four weeks from mid-August through early September, Mars

will be nearer to Earth, and appear bigger in a telescope, than it has since

1988. And at its very closest, it will be a hair closer than it has been in

many, many years.

But how many? Various different figures are being reported in different

places; some are clearly wrong. Sky & Telescope sorted through the situation

to find the authoritative answer.

 

On August 27, 2003, at 9:51 Universal Time, the centers of Earth and Mars

will be only 55,758,006 kilometers (34,646,418 miles) apart. The U.S. Naval

Observatory's MICA software and the Jet Propulsion Laboratory's DE406

planetary ephemeris agree on this value for the true geometric distance.

 

There has been some confusion about this because another authoritative

source, JPL Horizons gives a time five minutes earlier and a separation 86

km closer. But Horizons expresses all solar-system distances in " apparent "

rather than geometric form, which takes into account the motions of Earth

and Mars during the time it takes for light to travel between the two

bodies. There is no actual discrepancy.

 

Mars will indeed be truly close. As Belgian astronomers Edwin Goffin and

Jean Meeus wrote long ago, " In August, 2003, Mars will come closer to Earth

than at any time in the last several thousand years, and an even slightly

closer approach will take place in the year 2287 " (Sky & Telescope: August

1978, page 107). They also explained why. During recent millennia Mars's

orbit has been getting slightly more eccentric (elongated) due to the

gravitational attractions of other planets. Each passing century brings Mars

a little closer to the Sun at perihelion, and a little farther from the Sun

at aphelion.

 

 

On August 26-27, 2003 - the night of Mars's closest

approach to Earth since prehistoric times - Mars will present this face to

viewers in the Americas (around 12:40 a.m. Pacific Daylight Time, 3:40 a.m.

EDT). This computer graphic by Ralph Aeschliman includes the albedo markings

that ground-based telescopic observers typically see. It also shows some

surface relief, like the huge Valles Marineris canyon and neighboring

volcanoes. Courtesy Ralph Aeschliman.

 

 

 

 

 

But has Mars ever been this close before? Meeus partially addressed that

question in his 2002 book More Mathematical Astronomy Morsels. Working from

two papers by the late Pierre Bretagnon on long-term variations in the

planetary orbits, he found that Mars may have come closer to Earth about

73,000 years ago than it does this August.

 

Just as the Meeus book was rolling off the presses, several Web sites began

reporting an improved result. According to a calculation by the Association

of Lunar and Planetary Observers' Jeffrey Beish and James DeYoung, Mars came

a little closer to Earth in 57,537 BC. When he learned of that result Meeus

contacted Aldo Vitagliano, an expert in computational celestial mechanics at

the University of Naples, Italy. In April of last year, Vitagliano confirmed

that there was indeed a close approach in the year 57,538 BC (not 57,537

BC), but it did not quite beat the AD 2003 value.

 

Vitagliano's calculation required nearly three hours on an 800-megahertz

computer, and it entailed a simultaneous numerical integration of the

motions of all nine planets, the Moon, and three asteroids (Ceres, Pallas,

and Vesta). At first he adopted JPL's DE406 as the starting point; then he

repeated the calculation using JPL's earlier DE200. He even experimented to

see if omitting the asteroids and Pluto would make a significant

difference - it did not. Vitagliano concludes that the last time Mars came

so close was in 57,617 BC, when it passed within 55.718 million km of Earth,

a little closer than this year's 55.758 million km.

 

The ramifications for Mars observers are slight, of course. More important

for what your telescope will show on Mars are the quality of the atmospheric

seeing (the amount of heat-wave shimmering in Earth's atmosphere, which

changes from night to night and sometimes minute to minute), Mars's

elevation above the poor seeing near the horizon (Mars never gets very high

this year for observers at midnorthern latitudes), and the clarity of Mars's

own atmosphere (dust storms could haze it up at any time).

 

Nevertheless, a record is a record. Mars will be slightly closer than it has

been in 59,619 years. If our Neanderthal precursors had been able to use a

telescope in 57,617 BC, they could have seen Mars with an equatorial

diameter of 25.13 arcseconds (compared to 25.11 arcseconds this August).

Mars won't appear any larger until August 28, 2287, when earthlings will see

the red planet 25.14 arcseconds across.

 

Sky & Telescope senior editor Roger Sinnott will be watching this close

approach from his backyard observatory in the Boston suburbs.

 

 

--

 

 

> ------

>

>

>

>

>