C# Probability of Transform Colliding

Hi. I am trying to make two scripts. One below that is attached to an asteroid and moves it towards the target planet, and a second one to place on an observatory that would find the probability of the asteroid colliding with the target.

I know the script I have so far is completely wrong as the asteroid will always collide with the target every time. What I’m trying to do is get it to have a random probability of reaching the target and a second script that would calculate that probability. I am completely stuck and help to point me in the right direction would be much appreciated!!!

using UnityEngine;
using System.Collections;

public class Asteroid : MonoBehaviour {

	public Transform target;
        //Planet
	public float speed;
        //Speed of Asteroid

	void Update() {
		float step = speed * Time.deltaTime;
		transform.position = Vector3.MoveTowards(transform.position, target.position, step);
	}

void OnTriggerEnter(Collider other)
{
	if (other.gameObject.tag == "Planet") {
			print ("Asteroid Impact");
			Destroy (gameObject);  
                        //Destroys Asteroid
		}
	}
}

@Vuzok try adding a coroutine that gives you two random numbers 0 & 1, set the coroutine to wait in seconds so you have control over the intervals. now every time the number is 0 make the asteroid hit the target if it is 1 make it miss the target.