<p>Spaceref's <a href="http://spaceref.com/asteroids/nasas-tour-of-asteroid-bennu-selected-for-prestigious-computer-graphics-film-festival.html" rel="nofollow noreferrer">NASA's &quot;Tour of Asteroid Bennu&quot; Selected for Prestigious Computer Graphics Film Festival</a> says:</p>
<blockquote>
<p>It's hard to imagine what the surface of asteroid Bennu might look like - it's shortest distance from Earth still 250,000 miles away - but the video &quot;Tour of Asteroid Bennu&quot; brings us on a journey to see this landscape up close.</p>
<p>On August 9 and 11, 2021, the video produced at NASA's Goddard Space Flight Center in Greenbelt, Maryland, <strong>will be featured in the SIGGRAPH Computer Animation Festival Electronic Theater - a high honor for those in the graphic visualization field.</strong></p>
</blockquote>
<p>While the graphics are fantastic and the &quot;tour of Bennu's rocks&quot; is illuminating, the narration is... well... mostly serial mythology factoidisms.</p>
<p>Nonetheless the serial factoids about various rocks on Bennu make it worth a listen.</p>
<blockquote>
<p>The first stop is Simurgh Saxum. This prominent boulder defines the asteroid’s prime meridian, and serves as the basis of its coordinate system.</p>
<p>In Persian mythology, the Simurgh is a large and benevolent bird, and the possessor of all knowledge.</p>
<p>Saxum is Latin for “stone.”</p>
</blockquote>
<p><strong>Question:</strong> How does the rock Simurgh Saxum (-25.32°, 4.05°) on <a href="https://en.wikipedia.org/wiki/101955_Bennu" rel="nofollow noreferrer">101955 Bennu</a> define its prime meridian and serve as the basis for its coordinate system?</p>
<ol>
<li>Considering that its 4.05° longitude (shown in the video) is not on the prime meridian, how does it define it?</li>
<li>Either (at least) a second point is necessary to establish a coordinate system, or the spin axis is used to define poles, which is used in this case?</li>
</ol>
<hr />
<p>[<a href="https://i.sstatic.net/WZmdG.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/WZmdGm.jpg" alt="Screenshot from NASA Goddard's &quot;Tour of Asteroid Bennu&quot; https://youtu.be/QunVAWABQSc" /></a> <a href="https://i.sstatic.net/0dMfH.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/0dMfHm.jpg" alt="enter image description here" /></a></p>
<p><div class="youtube-embed"><div>
                <iframe width="640px" height="395px" src="https://www.youtube.com/embed/QunVAWABQSc?start=0"></iframe>
            </div></div></p>

CC BY-SA 4.0
2021-08-22T00:15:09.407Z
companion question: [How was a rock on the surface of asteroid 101955 Bennu first observed from Earth (Benben Saxum)?](https://astronomy.stackexchange.com/q/45419/7982)
uhoh
CC BY-SA 4.0
2021-08-22T01:13:26.290Z
I think the western edge of the rock defines 0 longitude, and the combination of that with the spin axis gives the coordinate system. The centre of the rock is at 4.05 degrees East. But I can't find a authoritative source stating that.
James K
<asteroids><coordinate><near-earth-object>
How does the rock Simurgh Saxum (-25.32°, 4.05°) on 101955 Bennu define its prime meridian and serve as the basis for its coordinate system?
uhoh
# How does the rock Simurgh Saxum (-25.32°, 4.05°) on 101955 Bennu define its prime meridian and serve as the basis for its coordinate system?

(Asked by: username_0 on 2021-08-22)

Spaceref's [NASA's "Tour of Asteroid Bennu" Selected for Prestigious Computer Graphics Film Festival](http://spaceref.com/asteroids/nasas-tour-of-asteroid-bennu-selected-for-prestigious-computer-graphics-film-festival.html) says:

> It's hard to imagine what the surface of asteroid Bennu might look like - it's shortest distance from Earth still 250,000 miles away - but the video "Tour of Asteroid Bennu" brings us on a journey to see this landscape up close.
>
> On August 9 and 11, 2021, the video produced at NASA's Goddard Space Flight Center in Greenbelt, Maryland, **will be featured in the SIGGRAPH Computer Animation Festival Electronic Theater - a high honor for those in the graphic visualization field.**

While the graphics are fantastic and the "tour of Bennu's rocks" is illuminating, the narration is... well... mostly serial mythology factoidisms.

Nonetheless the serial factoids about various rocks on Bennu make it worth a listen.

> The first stop is Simurgh Saxum. This prominent boulder defines the asteroid’s prime meridian, and serves as the basis of its coordinate system.
>
> In Persian mythology, the Simurgh is a large and benevolent bird, and the possessor of all knowledge.
>
> Saxum is Latin for “stone.”

**Question:** How does the rock Simurgh Saxum (-25.32°, 4.05°) on [101955 Bennu](https://en.wikipedia.org/wiki/101955_Bennu) define its prime meridian and serve as the basis for its coordinate system?

1. Considering that its 4.05° longitude (shown in the video) is not on the prime meridian, how does it define it?
2. Either (at least) a second point is necessary to establish a coordinate system, or the spin axis is used to define poles, which is used in this case?

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[[![Screenshot from NASA Goddard's ](https://i.sstatic.net/WZmdGm.jpg)](https://i.sstatic.net/WZmdG.jpg) [![enter image description here](https://i.sstatic.net/0dMfHm.jpg)](https://i.sstatic.net/0dMfH.jpg)

**Tags:** asteroids, coordinate, near-earth-object

> **Comments:**
> **username_0**: companion question: [How was a rock on the surface of asteroid 101955 Bennu first observed from Earth (Benben Saxum)?](https://astronomy.stackexchange.com/q/45419/7982)  
> **username_1**: I think the western edge of the rock defines 0 longitude, and the combination of that with the spin axis gives the coordinate system. The centre of the rock is at 4.05 degrees East. But I can't find a authoritative source stating that.  

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## 0 answers

