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Consider the standard action of $SO(2)\times SO(3)$ on$\mathbb{R}^5=\mathbb{R}^2\oplus \mathbb{R}^3$. We establish the existence of auniform constant $\mathcal{C}>0$ so that any $SO(2)\times SO(3)$-invariantRicci soliton on $\mathbb{S}^4\subset \mathbb{R}^5$ with Einstein constant $1$must have Riemann curvature and volume bounded by $\mathcal{C}$, andinjectivity radius bounded below by $\frac{1}{\mathcal{C}}$. This observation,coupled with basic numerics, gives strong evidence to suggest that the only$SO(2)\times SO(3)$-invariant Ricci solitons on $\mathbb{S}^4$ are round. Wealso encounter the so-called `pancake' ancient solution of the Ricci flow.

$SO(2)\times SO(3)$-invariant Ricci solitons and ancient flows on $\mathbb{S}^4$