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Mission to Mercury

By Sean McLachlan
Arizona Daily Wildcat
March 11, 1999
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Ian Mayer
Arizona Daily Wildcat

Professor of Planetary Sciences Robert Strom speaks about the proposed Messenger probe mission to Mercury in 2004. The last mission to the planet Mercury was the Mariner 10 mission in 1974.

A UA planetary scientist hoping to get a close-up look at the planet Mercury may achieve his dream - if NASA picks his project in June.

Planetary Sciences Professor Robert Strom last night complained about the lack of space probes to the innermost planet in the solar system.

He told a meeting of the University of Arizona's Students for Exploration and Development of Space that he is trying to get his Messenger probe accepted to fly on a Shuttle mission in 2004.

While the Moon, Venus and Mars have had dozens of probes scan and map their surfaces, the sole mission to Mercury was Mariner 10 in 1974. Strom was part of the project's imaging team.

"That's once, 25 years ago. That's despicable," he said.

Mercury is a bare and rocky planet that is only one-third the size of the earth. Its surface, covered in meteor craters, suffers vast differences in temperature because it is the closest planet to the Sun.

Its day side is blasted with radiation, rising to temperatures as high as 900 degrees - hot enough to melt lead.

As the planet rotates and the sun dips below the horizon, the heat dissipates through the almost non-existent atmosphere into cold space. The nighttime temperature dips to a chilly minus 300 degrees.

When Mariner 10 braved the harsh elements of the inner solar system, it was able to map less than half of the surface.

Strom started his study of Mercury as part of the Mariner 10 project team.

"Mercury is a huge gap in our understanding of the planets," Strom said.


Illustration courtesy of Robert Strom
Arizona Daily Wildcat

The Messenger space probe is designed with heavy shielding to protect it from the sun's extreme temperatures.

The Messenger project is directed out of the Johns Hopkins University's Applied Physics Laboratory. The probe will answer many questions that have been plaguing scientists since Mariner, he said.

One question - whether ice is in the shade of deep craters. Such "cold traps" remain at Mercury's nighttime temperatures even while the crater rim is sweltering in the Sun's rays.

Strom said he is especially curious to see what the unmapped portions of the planet look like.

Radar images of the unmapped side have indicated three unusual features, he said.

One may be a large impact crater, and another may be a 360-mile wide volcano reaching down to the planet's iron core, he said.

The other radar emanation looks like nothing anyone's ever seen before, he said.

The probe may also clarify Mercury's wild geologic history, he said.

Strom said the planet sustained a heavy bombardment of meteors, creating a cratered, dusty surface similar to our Moon.

As the molten planet cooled, it shrunk in size. Plains were pushed up and ridges formed. Around this time, a giant meteor impact sent shock waves through the planet that pushed up mountains on the other side.

Those mountains thrust up to a height of one to six miles almost instantly, he said.

"That would be like forming the Catalina mountains in a second. Boop! There they are and there you aren't," he said.

While evidence of the immense impact can be clearly seen on the Mariner photographs, most other aspects of Mercury's history are only vaguely known, Strom said.

"Anytime I discuss this in my geology class I get nervous because I have a gut feeling that this is all wrong," he said.

The Messenger probe is competing with several other missions for approval by NASA, but Strom said he hopes that it will be approved after officials see the array of questions it would answer.

If so, a lifelong study which started more than 25 years ago will culminate in a second mission to Mercury.

"This has got to go," he said. "This is my last hurrah - my last chance to see Mercury."