involved in how the scale came to be accepted by the scientists and organizations responsible for keeping track of Near-Earth Objects (NEOs). NEOs are sun-circling comets and asteroids -- chunks of rock and iron -- that spend some portion of their time relatively near our planet, occasionally developing a gravitational propensity for wreaking a little terrestrial havoc. Many scientists believe a large asteroid was responsible for the demise of the dinosaurs.
Brian Marsden, director of the Minor Planet Center, told space.com that the Torino Scale is "largely irrelevant," charging that it does little to inform the public and is an oversimplification for serious researchers. He is also baffled over how the scale was loosely adopted by the International Astronomical Union (IAU), the organizing body that oversees the Minor Planet Center, a clearinghouse for all such information.
While the Torino Scale's official status within the IAU is unclear, most NEO researchers say it has the potential to be useful, even if they have concerns about its adoption.
The impact of "Deep Impact"
While few prominent scientists in the NEO community share Marsden's highly critical view, he is a key player in the search for space rocks. Besides directing the Minor Planet Center, he is known for having triggered the first widespread fears of a so-called "Deep Impact" with his announcement in March 1998 that asteroid 1997 XF11 could strike the Earth.
The risk for XF11 was subsequently found to be zero after fresh data was studied. Many NEO researchers argue that the public was needlessly alarmed -- by the next day, the new calculations had put the threat to rest.
"A number of people in the NEO community have issue with the way Brian handles observations and orbital predictions," said Kelly Beatty, senior editor of Sky & Telescope magazine and a contributor to the development of the Torino Scale.
But Marsden says the announcement of XF11 was the very thing that brought out the additional data that eliminated the threat. In the end, he says, the publicity helped improve NEO research.
To be sure, XF11 was a catalyst for scientific discourse that eventually contributed to the adoption of the very Torino Scale that Marsden criticizes. The publicity surrounding XF11, and the confusion generated in the scientist-journalist-public communication pipeline, were key events that encouraged the NEO community to support Binzel's Torino Scale.
It's just a tool
Binzel characterizes the colorful, numbered chart as a useful tool that puts the vast majority of possibly threatening asteroids in Category Zero, which he says appropriately downplays the public perception of any miniscule threat.
On the Torino Scale, Category Zero states the likelihood of a collision is "well below the chance that a random object of the same size will strike the Earth within the next few decades." (The implication being that there is always a chance we will be sucker-punched by an asteroid that has not yet been discovered.)
"We do not have to create public alarm every time we discover an object that has the most remote chance of striking Earth," Binzel told space.com in a telephone interview. Yet he firmly agrees with Marsden that objects falling into Category Zero need further attention. This category was not designed to remove objects from the scientists' mental radar, Binzel says, but rather to earmark them for more study. If further observations warrant, an object can move upward on the scale accordingly.
Marsden, however, says the scale's ambiguity makes it difficult to decide where an object belongs, adding that the scale does not properly consider objects that may present a threat many decades into the future and therefore require significant additional observations.
Further, as Marsden sees the system, most NEOs won't reach level one or higher until a second round of calculations is made. But if a particular NEO is buried in the catchall Category Zero, its orbital calculations are not in need of official IAU peer review, as defined by the Torino Scale's guidelines. Therefore, researchers are free to publicize their findings, as has been done in at least one case since the Torino Scale went into effect, of what everyone would agree is an object with a relatively low-level threat.
On the other hand, calculations of an NEO that merits a ranking of one or higher are supposed to be reviewed by the IAU prior to being published. Marsden argues that the calculations do not need reviewing, as prior announcements in the field have not been faulty because of any miscalculations.
Marsden says previous NEO announcements, regardless of their public effect, have increased awareness within the NEO community of the need to use all possible means to make additional calculations once an object has been discovered.
"The public is more of a problem," Marsden says, "because they have unfortunately received the messages that astronomers make mistakes in their calculations (which is not true) and that they fight with each other (which is)."
Binzel approaches his hazard scale from a whole different trajectory, stressing that there are other means of communication between scientists. The Torino Scale is not intended to facilitate that process, he says, but rather to communicate between scientists and the public. Those outside the NEO community, he points out, cannot be expected to comprehend the complexity of the individual calculations. Still, the scale's apparent adoption by the IAU means researchers do have to consider it.
"So I think the disagreement is a question of what language we use, what method we use to draw attention in the scientific community to an object that urgently needs follow-up measurements," Binzel said.
Torino, the teenager
In talking with several experts, it becomes clear that the Torino Scale is like a typical teenager: It has not yet staked out who or what it really is, or where it is going. But most NEO researchers expressed optimism that the scale -- or some grown-up version of it -- will stick.
Its exact role, however, remains to be determined. At Liverpool John Moores University, Dr. Benny Peiser points out that the most important aspect surrounding a potentially hazardous asteroid is data, and more of it, which is the only way to determine or eliminate the ultimate threat.
"The Torino Scale was, I guess, mainly created as a sedative for the general public," Peiser said.
Meanwhile, Binzel says the scale's real intention is as a tool for journalists. While this was not the focus of press releases regarding the scale, Binzel did seek input on the idea from three science journalists prior to presenting the revised version in Italy (a previous version in 1995 was never adopted).
Beatty, the Sky & Telescope editor, was one of those contributors, and he says Binzel's first challenge is to get the astronomical community to adopt the scale, and then the journalists will follow. Beatty said some sort of resolution might come at an IAU meeting scheduled for August.
"Assuming the astronomical community gets behind it, then it creates a metric that journalists can rely on," Beatty said. "My take is that this is version 1.0 of this scale. I suspect that as our knowledge becomes more complete... we may find the scale defined differently to represent the hazards."
While willing to consider altered future versions, Binzel said, "we don't want to make changes and revisions that end up confusing the public. If it doesn't work in its test phase for the next several years, we can think about ways to change it."
Meanwhile, out there in the grand void are a handful of comets and asteroids with our collective names etched all over them. Similar objects have hit Earth before, others will arrive in the future. While pure chance could cause such a catastrophe tomorrow, odds are such a thing won't happen for a very long time.
Providing this perspective -- in a simplified way to the general public -- is the primary purpose of the Torino Scale, Binzel said. "If I tell you an object is a 1 on a 10-point scale, where 10 is total disaster, immediately you know there is no major cause for public concern."
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